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FOREWORD
The U.S. Environmental Protection Agency was created
because of increasing public and government concern about the
dangers of pollution to the health and welfare of the American
people. Noxious air, foul water, and spoiled land are tragic
testimonies to the deterioration of our natural environment. 1
The complexity of that environment and the interplay of its
components require a concentrated and integrated attack on the
problem.
Research and development are the necessary first steps in
problem solution, and involve defining the problem, measuring
its impact, and searching for solutions. The Municipal
Environmental Research Laboratory develops new and improved
technology and systems to prevent, treat, and manage wastewater
and solid and hazardous waste pollutant discharges from
municipal and community sources, to preserve c >d treat public
drink water supplies, and to minimize the adverse economic,
social, health, and aesthetic effects of pollution. This
publication is one of the products of that research and is a
most vital communication link between the researcher and the
user community.
The innovative and alternative technology provisions of
the Clean Water Act of 1977 (PL 95-217) provide financial
incentives to communities that use wastewater treatment
alternatives to reduce costs or energy consumption over
conventional systems. Some of these technologies have been
only recently developed and are not in widespread use in the
United States. In an effort to increase awareness of the
potential benefits of such alternatives and to encourage their
implementation where applicable, the Municipal Environmental
Research Laboratory has initiated this series of Emerging
Technology Assessment reports. This document discusses the
applicability and technical and economic feasibility of using
aquaculture systems for municipal wastewater treatment
facilities.
Francis T. Mayo
Director
Municipal Environmental Research
Laboratory
111
I
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ABSTRACT
Aquaculture involves the production of aquatic organisms,
both flora and fauna, under controlled conditions, primarily
for the generation of food, fiber, and fertilizer. The scope
of this assessment is limited tovaquacuLture systems for
domestic wastewator treatment. Wastewater aquaculture involves
a variety of organism*. Aquatic macrophytes (water tolerant
vascular plants), finfish, invertebrates, and integrated
systems are the major components considered in this assessment.
Recently, increased attention has been given to the use of
designed aquaculture systems for improvement of water quality
and wastewater treatment system capacity. Aquaculture systems
are being used to achieve secondary and advanced wastewater
treatment. Many current systems use aquaculture components for
removal of specific pollutants such as biochemical oxygen de-
mand, suspended solids, nutrients, or metals, or are designed
as a polishing step after conventional forms of treatment.
Experts in the field recommend that current research and
development efforts should be concentrated on aquatic macro-
phytes. They conclude that aquatic plant systems, particularly
water hyacinths, are ready for routine use in municipal waste-
water treatment, at least within the geographical areas where
such plants grow naturally. Pish, invertebrates, and inte-
grated systems are in the exploratory or developmental stage
and, as such, are not ready for routine use.
All aquatic macrophytes have wastewater treatment
potential. The greatest emphasis has been placed on the utili-
zation of water hyacinths and, to a lesser extent, duckweeds.
Most of the information now available on the performance of
aquatic plants in wastewater treatment processes is based upon
these two species.
Water hyacinths thrive in an environment where the average
air temperature ranges from 4.4 to 35°C (40 to 95°F). Year-
round plant growth in the natural environment is therefore
restricted to southern Florida and southern Texas. An aquacul-
ture system may also be installed for seasonal use such as for
nutrient removal during the spring and summer months. Aquacul-
ture systems may also be covered to provide an artificial
environment.
1v
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The status of water hyacinths in wastewater treatment has
progressively developed during the past few years of research.
Water hyacinths have been extensively studied at the laboratory
level and tested at the pilot scale level. Continuation of
these efforts has produced a number of full-scale experimental
and demonstration systems. The research completed on inverte-
brate, fish and integrated systems is limited and only includes
bench and pilot level studies.
Aquaculture wastewater treatment systems consist of one or
more shallow basins, ponds, or raceways in which one or several
species of aquatic organisms are cultured. The constructed
basins and the systems themselves are generally similar in
concept to those used in wastewater treatment pond technology.
Aquatic plant system's treatment mechanisms are functions
of the existing physical conditions, the biological habitat and
the removal of soluble substances from the water by plant
uptake. The primary treatment mechanism operative in animal-
based aquaculture treatment systems is the control of suspended
solids. By stocking and culturing fish and/or invertebrates in
wastewater treatment ponds, simple organics, algae and
suspended particuates are converted into animal tissue*
Under most conditions, the cost of an aquaculture system
is less than or equal to the cost of a conventional system.
Conversion of an existing pond system would result in signifi-
cantly less cost than an equivalent conventional system.
Energy demands for an aquaculture system are significantly less
than a conventional system by as much as 80 to 90 percent.
Aquficulture systems are usually limited to suburban and
rural communities because of the large land area requirements.
Theoretically, an aquaculture system can be designed for any
capacity, but because the system is land intensive, the cost
and availability of land are limiting factors for use in urban
settings.
Recommendations for future aquaculture research include
optimization of basin design, testing of design criteria,
documentation of costs and labor requirements, and the
development of alternative plant systems*
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CONTENTS
Disclaimer 11
Foreword Ill
Abstract 1v
Figures 1x
Tables x
Participants . . x111
Section 1. Technology Description ... 1
Introduction 1
Detailed Description 3
Aquatic Plants 6
Water Hyacinth 6
Duckweeds. 11
Fish 12
Invertebrates 14
Integrated Systems 14
Culture Basins 14
Common Process Modifications 16
Section 2. Recommendations 18
Section 3. Developmental SUtus of Aguaculture Systems. . . 20
Summary of Research Findings .20
Aquatic Macrophytes. .... 20
Summary of Research Findings 20
Bench Scale Research 20
Pilot Scale Research ..23
Full-scale Facilities/Aquaculture
Fact Sheets 28
Invertebrates 39
Bench Scale Research 39
Pilot Scale Research 40
Fish 41
General Studies 41
Pilot Scale Research 42
integrated Systems 45
General Studies 45
Available Equipment/Hardware 47
v1
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Section 4. Technology Evaluation 51
Process Concept 51
Aquatic Plant Systems 51
Aquatic Animal Systems . , 53
Process Capabilities and Limitations 56
Aquatic Plant Systems 56
Performance 56
Temperature and Location Constraints . . 56
By-Product Recovery ...57
Reuse Constraints 57
Evapotranspiration 57
Odor Problems and Control 57
Mosquito Problems and Control 57
Wind Problems and Control. 58
» Land Requirements 58
! Legal Constraints 58
Aquatic Animal Systems 58
Performance 58
Dissolved Oxygen Constraints 59
Temperature Constraints 59
By-Product Recovery 59
Reuse Constraints 60
Land Requirements 60
Legal Constraints, .....61
Marine vs. Freshwater Systems. ..... 61
Culture Constraints 61
Design Considerations 62
Location-Climate-Temperature 64
Site Requirements 64
Land Requirements 64
Wastevater Characteristics 65
Pretreatment ...66
Post-Treatment 66
Pond Size, Number, and Configuration .... 66
Organic and Surface Loading Rates 66
Hydraulic Residence Time 68
Hydraulic Loading Rates . 68
Recovery of Biomass 68
Other Parameters 69
Energy Analysis ..69
Operation and Maintenance Requirements 72
Cost Analysis 74
Section 5. Comparison with Equivalent Conventional
Technology 87
Cost Comparison 87
Energy Comparison ...92
vii
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Section 6. National Impact Assessment ........... 98
Potential Market 98
Cost and Energy Impact 99
Cost 99
Energy 101
Perspective 101
Cost 101
Energy 103
Marketability .103
Section 7. List of References and Contacts 104
V111
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FIGURES
Mumh«r
1
3
4
5
6
7
8
9
10
11
12
13
Page
*
Process Flow Diagrams - Aguaculture Systems
for Wastewater Treatment 4
Aquatic Plant Wastewater Treatment System
Schematic and Flow Diagram 5
Morphology of Water Hyacinth and Duckweed .... 8
A Network of Possible Water Hyacinth Processes
and Products 49
Annual Average Cost Comparison.
88
Average Annual Cost Comparison - Advanced
Treatment 89
Capital Cost Comparison - Secondary Treatment . . 90
Capital Cost Comparison - Advanced Treatment. . . 91
Annual O&N Cost Comparison - Secondary
Treatment 93
Annual O&M Cost Comparison - Advanced Treatment . 94
Comparison of Energy Demands - Secondary
Treatment 96
Comparison of Energy Demands - Advanced
Treatment 97
Water Hyacinth's Approximate Climatic Boundary. .100
1x
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TABLES
Number Page
1 Selection of Potential Aquatic Macrophytes for
use in Aquaculture Wastewater Treatment Systems. 7
2 Dry Weight Composition of Whole Water Hyacinth
Plants Grown in Wastewater 10
3 Dry Weight Composition of Duckweed Plants Grown
in Wastewater 11
4 Fish Species Used in Aquaculture Wastewater
Treatment Systems 13
5 Percent Reductions in Wastewater Character-
istics Utilizing Water Hyacinths under Batch
Laboratory Conditions 22
6 Capability of Water Hyacinths to Remove Various
Chemical and Metal Pollutants from Waters. ... 22
7 Summary of Nutrient Data from Three Test Ponds
During Phase 3 of the Pilot Studies at the
University of Florida from July 1973 to June
1974 25
8 Summary of Average Water Quality Parameters
Affected by Water Hyacinth Treatment in Pilot
Studies at Williamson Creekt Texas ....... 26
9 Summary of Design and Performance Character-
istics of the Pilot Wasteweter Treatment
Systems Using Aquatic Plant? studies by NASA/
NSTL 27
10 Summary of Water Quality Parameters Resulting
from a Three-Stage Batch Laboratory Experiment
Culturing a Marine Algae (Tatraaalmia) and
Brine Shrimp for 96 Hours 39
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26
27
28
29
30
31
32
Annual Operation and Maintenance Cost for an
Aguaculture System 82
Estimated Costs for an Aquaculture System, Case
1, 4000 cu m/day 84
Estimated Costs for an Aquaculture Syetem, Case
2, 4000 cu m/day
Estimated Costs for an Aquaculture System, Case
3, 4000 cu m/day
Comparison of Aquaculture and Conventional
Secondary System Annual Energy Requirements. . ,
Estimated Number of Treatment .Plants to be
Constructed during the Years 1978 to 2000
within Climatic Zones Favorable to Hater
Hyacinths
85
86
95
99
Estimated Annual Energy Demands for the Antici-
pated Treatment Plants, 1978-2000, Btu/year. . . 102
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SECTION 1
TECHNOLOGY DESCRIPTION
INTRODUCTION
Aquaculture involves the production of aquatic organisms,
both flora and fauna, under controlled conditions, primarily
for the generation of food, fiber, and fertilizer. A review of
the developmental history and current worldwide practices in
aguaculture production systems has been provided by Bardach et
al. (Reference 1). Aquatic biological systems are employed in
a variety of wastewater treatment processes, such as activated
sludge, trickling filters and lagoons. The use of aquacultural
concepts employing higher aquatic plants and animals for the
treatment and reuse of municipal wastewaters is now encouraged
by federal legislation under the provisions of the Federal
Water Pollution Control Act Amendments of 1972 (PL 92-500) and
the Clean Water Act of 1977 (PL 95-217). Wastewater aqua-
culture is very broad in scope involving a variety of
organisms, both freshwater and marine environments, as well as
wastewater recycling through natural aquatic habitats
(Reference 2). Aquatic macrophytes (water tolerant vascular
plants), finfish, invertebrates, and integrated systems are the
aquacultural components considered in this assessment. A
separate technology assessment covers the subject of wetland
systems used for wastewater treatment (Reference 3), and thus
are not specifically discussed in this report.
Wastewater aquaculture systems are not a new concept. In
many parts of the world, fertilization of ponds with human and
animal wastes to increase growth and production of fish has
been practiced for centuries (Reference 4). A review of sewage
fertilization in fish culture was published by Allen (Reference
5). Recently, increased attention has been given to the
improvement of water quality and the waste treatment system
capacity by use of designed aquaculture systems. Conferences
have stressed the use of wastewaters in food and fiber
production (References 6 and 7), and emphasized aquatic biolo-
gical systems as wastewater purification schemes (References 8
and 9). In 1978, Duffer and Noyer reviewed the developmental
status of the aquaculture alternative for wastewater treatment
with emphasis given to the reduction or fate of pollutants
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(Reference 10). The proceedings of a seminar (Reference 11)
and engineering assessment on wastewater aguaculture systems
(Reference 12) in 1979 defined the status of aquaculture
technologies to determine if they were ready for use in
municipal vastewater treatment.
The conversion of wastes by aquatic organisms relies on
the same basic biological principles used in aquaculture
production systems. In this assessment, the scope is limited
to those systems that emphasize the culture of aquatic
organisms for w.astewater treatment and management. Biomass
production or recovery of some other beneficial product is a
secondary feature. However, potential economic return from a
harvested by-product to offset the costs of wastewater treat-
ment could serve as an incentive to use these alternative
systems.
Aquaculture systems are being used for all phases of
wastewater treatment from secondary through advanced wastewater
treatment. Many current systems use aquaculture components for
removal of specific pollutants such as biochemical oxygen de-
mand (BOD), suspended solids (SS), nutrients or metals, or are
designed as a polishing step after conventional forms of treat-
ment. The fundamental purpose of aquatic plants and animals,
and their management in aquaculture systems, is to improve the
rate and/or reliability of one or more of the contaminant
removal mechanisms in the aquaculture treatment system
(Reference 13).
Interest in aquaculture processes for wastewater treatment
is fostered not only in the acknowledgement that wastewater can
be viewed as a resource, but also that these processes can be
adapted to low technology systems. Although more land
intensive, aquaculture systems can potentially be cost compet-
itive with conventional treatment. In some applications they
use less energy and non-renewable resources when compared to
conventional treatment schemes.
A wide range of managed aquatic biological systems have
been considered and investigated for the purpose of wastewater
treatment. Systems have included ponds, basins, raceways and
other structures which utilize various combinations of aquatic
plants and animals. A technical advisory group headed by
Duffer and Barlin was established in 1979 to aid in objectively
assessing the potential for development of wastewater
aquaculture treatment systems. Based on available technology
and potential for early payoff, this group reported that the
current research and development efforts should be concentrated
on aquatic macrophytes (Reference 2). In 1980, Reed et al.
concluded that aquatic plant systems, particularly water hya-
cinths, are ready for routine use in municipal wastewater
- wL,froat
•it •vaiUbU copy.
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treatment, at least within the geographical range where such
plants grow naturally. Fish, invertebrate, and integrated
systems are all still in the exploratory or developmental stage
and as such, are not ready for routine use (Reference 14).
Systems involving higher forms of animals are generally effi-
cient, however they require more land or are more difficult to
control than their aquatic plant counterparts. Nevertheless,
animal-based systems may find wastewater treatment applications
where use of an aquatic plant is limited due to climatic or
other constraints (Reference 15).
DETAILED DESCRIPTION
Aquaculture wastewater treatment systems consist of one or
more shallow basins, ponds, or raceway in which one or several
species of aquatic organisms are cultured. The constructed
basins and the systems themselves are generally similar in
concept to those employed in wastewater treatment pond
technology (Reference 14). Frequently aquatic plants or fish
are stocked in the final cells of existing wastewater stabili-
zation ponds. The major physical difference between aquacul-
ture systems and stabilization ponds is the presence of higher
aquatic plants and/or animals in addition to suspended plank-
tonic species such as algae (Reference 13).
Aquatic plants, particularly water hyacinths, are used to
treat raw wastewater as well as effluents from various stages
of conventional treatment units. The most common system
incorporates a stabilization pond followed by aquatic plant
culturing basins in series (Reference 16). Animal-based
aquaculture wastewater treatment systems have been applied to
secondary effluent or to its equivalent to produce the effluent
quality of secondary or advanced treatment levels. A schematic
process-flow diagram of aquaculture wastewater treatment
systems is illustrated in Figures 1 and 2.
The selection of aquatic organisms for use in wastewater
treatment is based on the degree of pretreatment, the required
treatment level, by-product recovery, and the environmental
requirements of the candidate species (Reference 13). A
summary of selected references dealing- with the environmental
requirements of potential plant and animals species to be used
for the treatment of wastewater has been published by the
California State Water Resources Control Board. As part of an.
overall assessment of wastewater aquaculture (Reference 17),'
these annotated bibliographies deal with the physical,
chemical, and biological parameters of aquatic plants
(Reference 18), fish (Reference 19), crustaceans (Reference
20), and freshwater bivalves (Reference 21).
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IKPROVING WATER QUALITY
PRIMARY
TREATMENT
SECONDARY
TREATMENT
ADVANCED TREATMENT
HASTEWATER INFLUENT
EFFLUENT VARIATIONS:
Post-Treatment
Discharge
Reuse
FIGURE 1. Process flow diagramt - aquacuttur* systems for wastswatsr treatment.
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Watar Hyacinth Covar
Muant
PoaaMa Inftuanta:
1. Raw Sawaga
2. Primary Traatad
Waatawatar
3. Sacondary Traatad
Waatawatar
. AquaeuMura Baafei
Otfiar Aquatic Ptanta:
1. Duofcwaad
2. Ftoattao Ptanta
4. EaiafQarrta
A. Schematic
PoaaMa Effluant Oiapoaafc
1. Poat-traatmant
2. Dfaoharga
3.Rauaa
WeWDirtrtHitor
Ftow Pattam Vartattona:
1. SarlaaFtow
2. Paralal Ftow
^Barrier
Othar Physical Variation*
1. Slngto Gal Pond
2. MuMtota Pond
3. Convartad Stabteatton
B. Flow Diagram
FIGURE 2. Aquatic plant waatawatar traatmant ayatam aohamatic and flow diagram.
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Aquatic PIante (MaerophyfcaB)
All aquatic nacrophytee (water tolerant vascular plants)
have was-tewater treatment potential. Selection of plant
species is dependent on the type of aquatic environments
necessary to achieve the vastewater treatment objectives and
the potential of the plant species to reliably provide
necessary components of these environments (Reference 13). A
representative variety of aquatic macrophytes that have been
studied, or show potential for the reclamation of vastewaters
ire presented in Table 1. Many aquatic plants need to be
tested for wastewater treatment effectiveness, climatic
limitations, commercial uses, and yield. The wastewater treat-
ment effectiveness of a wide range of non-aquatic plants
utilizing an intensive hydroponic culture system is being
tested by Jewell of Cornell University (personal communi-
cation). Emphasis has been placed on non-food crops of high
value such as ornamentals.
The greatest emphasis has been placed on the utilization
of water hyacinths and, to a lesser extent, duckweeds. Most of
the information now available on the performance of aquatic
plants in wastewater treatment processes is based upon these
species. The characteristics of water hyacinths and duckweeds
which make these plants suited for wastewater application have
been summarized by several researchers (References 22, 23 and
24) and include the following:
o Rapid vegetative growth rates and productivity
especially when grown in waste-enriched waters;
o High nutrient and mineral absorption capabilities;
o Harvesting accessibility; as these plants are not
rooted, their floating nature facilitates mechanical
removal;
o Reasonable nutritive value and inorganic content for
potential by-product and economic recovery (animal
feed, compost, methane production);
o Extreme hardiness, even in raw sewage;
o Resistance to diseases and insects.
Water Hyacinth, Eichornia crassipies—
Water hyacinth is a perennial freshwater plant with
rounded, upright, shiny green leaves and spikes of lavendar
flowers. The morphology of a water hyacinth is illustrated
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TABLE 1. SELECTION OF POTENTIAL AQUATIC MACROPHYTES FOR USE IN
AQUACULTURE WASTEWATER TREATMENT SYSTEMS
Common Name
Floating Aquatic Plants
Hater hyacinth
Duckweed
(Lemnaceae family)
Water primrose
Hater lettuce
Hater fern
Hater velvet
Alligator weed
Submerged Aquatic Plants
Pond weeds
Oxygen weed
Coontail
Watermilfoil
Scientific Name
Eichhornia crassipes
Lemna 6pp.
Spirodela spp.
Holffia spp.
Ludwigia spp.
Pistia stratiotes
Salvinia spp.
Azolla spp.
Alternanthera philoxerides
Potamoggton spp.
Elodea spp.
Ceratophyllum spp.
Hyriophyllum spp.
schematically in Figure 3. The petioles are spongy, with many
air spaces, and are often swollen, contributing to the bouyancy
of the plant in its free-floating state. Roots, leaves, and
inflourescence (the characteristic arrangement of flowers on a
stalk or cluster) arise from a vegetative stem or rhizome
having short internodes. Underwater rhizomes, or stolons,
connect plants to each other and dense mats of plants
frequently form.
Native to South America, water hyacinths occur in slow
moving or stagnant freshwater* throughout the tropics and
subtropic regions of the world. The geographical area in which
these plants thrive is bounded by 32DN and 32°S latitude.
Introduced into the United States in 1884, the species spread
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Leaves
Roots
Fronds
WATER HYACINTH
(Elchhornia crasslpes)
Water Surface
Rhizome
DUCKWEED
(Lemna 8pp.)
(Spjrodeja 8pp.)
(Wqlffia SppJ
FIGURE 3. Morphology of water hyacinth and duckweed.
8
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-••V-*.-.'-."--.
rapidly and became established in waterways of several southern
states. Cue tc its rat-id vegetative growth and prolific
nature/ infested waterways prevented water movement and
navigation. Weed control programs, dating back to 1SCO,
involved nechanical procedures later replaced by the use of
herbicides. These efforts involved the expenditure of millions
of dollars and generated extensive technical literature.
The water hyacinth is probably the mcst intensively
studied aquatic plant to date. In 1948, Penfcund and Earle
conducted life history study of hyacinths (Reference 25).
Pieterse published a review article in 1975 on water hyacinths
covering all aspects of research that have been accomplished,
including sections on general botany, ecology and plant growth;
chemical biological and mechanical control; chemical
composition; utilization of the plant for by-products, and use
for the removal of minerals and pollutants from wastewater
(Feferer.ee 26).
There are several environmental factors affecting water
hyacin h growth. The most significant is temperature. The
optimum water temperature ranges from 20° to 30°C, with growth
ceasing below 10°C and above 40°C. Freezing temperature will
kill the leaves and steins of the plant above water. However,
the plant can regenerate from the rhizomes when weather
conditions improve, providing the rhizomes are not frozen. Air
temperatures lower than -2.2"C will usually kill the rhizomes
(Reference 25). This restricts the area of uniform year-round
plant growth in the natural environment to southern Florida and
southern Texas (Reference 27). Throughout the remainder of the
United States, active growth occurs from seven to ten months
per year.
Water hyacinths are also intolerant to salt water, and
will die in waters with salt concentrations of 2.2 parts per
thousand (Reference 26). Hyacinth plant growth ie also related
to the available concentration of nutrients, particularly
nitrogen, in the water (Reference 22).
Water hyacinth growth rates and productivity have been
investigated by several researchers. Unfortunately, many
different terms and units of measure are used to describe plant
production, resulting in data difficult to compare. Also wide
variations for growth responses contained in the literature are
partly due to differences in the environments encountered in
natural systems and in the enriched media provided by waste-
watsr (Reference 29).
Early growth rate studies by Penfound and Earle (Reference
25) in natural environments were used by Westlake in estimating
the annual productivity of water hyacinth to be 10 to 30 metric
Reproduced Irora
\ best available copy.
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tons/ha, dry-weight, with projections of possible maximum
annual production rates of 100 to 136 metric tons/ha/yr, dry-
weight, under ideal conditions (Reference 30). A study by
Wcoten and Dodd found a production of 27 metric tons of organic
matter/ha in only 105 days (Reference 31). Wolverton and
McDonald later projected an annual productivity of 140 dry
metric tons/ha from growth rate studies at a wastewater lagoon
in southern Mississippi (Reference 32). Measured yields of 80
dry metric tons/ha/yr were reported in central Florida under
optimum conditions (Reference 33).
Besides being one of the most productive photosynthetic
plants, water hyacinths are prolific, reproducing primarily by
vegetative means. Cornwell determined that the average
doubling rate for a mass of hyacinths was approximately six
days (Reference 34). It was estimated that in an eight month
growing season, ten plants could produce 600,000 and cover one
acre of water (Reference 25). Individual plant measure from 50
to 120 cm, root tip to the top of the flower cluster, when
grown in wastewater (Reference 35).
The major constituent of water hyacinth biomass is water,
contributing approximately 95 percent of the weight of the
plant. The dry weight composition of water hyacinths removed
from a wastewater treatment system is presented in Table 2.
TABLE 2. DRY WEIGHT COMPOSITION OF WHOLE WATER HYACINTH PLANTS
GROWN IN WASTEWATER (References 11 and 32)
Percent of Dry Weight
Parameter
Crude Protein
Fat
Fiber
Ash
Carbohydrate*
Rjeldahl Nitrogen (as N)
Phosphorus (as P)
Average
18.1
1.88
18.6
16.6
44.8
2.90
0.63
Range
9.7 -
1.59 -
17.1 -
11.1 -
36.9 -
1.56 -
0.31 -
23.4
2.20
19.5
20.4
51.6
3.74
0.89
*Computed by mass balance
10
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Duckweeds-
Members of the duckweed family (LfiJDAa spp., Spirodela
spp., and Wolffia spp.) are all small green plants, with
individual structures and fronds, less than one centimeter in
length. The morphology of duckweed is illustrated in Figure 3.
The plants float at or just below the surface of relatively
still, fresh water. Occurring world-wide, duckweeds have a
wider geographic range than water hyacinths. They vegetate at
temperatures above 1° to 3° and winter well (Reference 24).
Some duckweeds grow in brackish water.
Duckweeds (L£mn& spp.) grown at 27°C under laboratory
conditions in wastewater effluent were reported to double in
frond number, and thus in area, every four days (Reference 36).
The dry weight of duckweed grown under these conditions was
0.25 metric tons/ha. Ryther reported an annual yield of 12.2
metric tons/ha/yr., dry weight, for L&DHA sp. in a medium of
enriched well water under optimum conditions (Reference 33).
Hillman and Culley reported an annual dry-weight production of
mixed duckweed populations on a wastewater lagoon in the
southern United States of 17.6, with a maximum of 24.5, dry
metric tons/ha/yr (Reference 24).
Duckweed, like water hyacinth, contains approximately 95
percent water in the plant tissue. The composition of this
tissue is summarized in Table 3.
TABLE 3. DRY WEIGHT COMPOSITION OF DUCKWEED PLANTS GROWN IN
WASTEWATER (References 24, 29, 37)
Percent of Dry Weight
Parameter
Crude Protein
Fat
Fiber
Ash
Carbohydrate*
Kjeldahl Nitrogen (as N)
Phosphorus (as P)
Average
38.9
4.9
9.4
15.0
35.8
5.91
1.37
Range
32.7 -
3.0 -
7.3 -
12.0 -
-
4.59 -
0.80 -
44.7
6.7
13.5
20.3
-
7.15
1.8
*Computed by mass balance
11
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Fish
Fi£h species for culture in wastewaters historically have
reen chosen for production of a valuable product rather than as
a means of wastewater treatment. Limits in culture capability
have contributed to the complexities of obtaining both
objectives (Reference 10). Species of fish that have been used
in wa&tewater treatment experiments are described in Table 4.
Fish biomass produced by feeding on an algae and inverte-
brate biomass represents a removal of nutrients that would
otherwise be discharged in the effluent. Fish species that
feed lower on the food chain offer greater potential for the
treatment of wastes and resource recovery. Polyculture
systems, the use of different trophic levels, combine severe!
species of fish for wastewater treatment. The combination of
pure plankton feeding fishes, filamentous algae eaters, bottom
feeders, or scavengers also offers greater treatment potential
than a monoculture system.
Because fish physiology is regulated to a great extent by
the aquatic environment with which they are in contact, the
selection of fish species for the treatment of wastes requires
an understanding of the environmental requirements of the
candidate species (Reference 19). As fish are temperature
conformers, temperature has the greatest effect on the
physiology of fish of any of the environmental variables.
Thus, water temperature has a significant effect on food
ntake, digestion, growth, and behavior. Dissolved oxygen is
other of the limiting parameters for fish. For each species
ere exists a critical oxygen level, but in most cases,
dissolved oxygen concentrations less than 2 mg/1 are limiting
to fish and concentrations below 5 mg/1 promote slow growth.
Other physical parameters to be considered include light
intensity, photoperiod, and gas supersaturation.
The nitrogenous compound ammonia is highly toxic to fish.
Sublethal or lethal levels may accumulate in wastewater due to
either the metabolic wastes excreted by aquatic animals or from
human wastes or other sources. The pH tolerance of fish ranges
from 6.5 to 9 and will not be a significant parameter under
normal conditions. Other chemical parameters, such as
salinity, heavy metals, toxics, etc., also affect the growth
and survival of fish.
A group of fishes known as Chinese carp, which include the
silver, bighead, black, and grass, carp, and the European
common carp (see Table 4) may be considered the most likely
candidates for achieving the objective of wastewater treatment.
These fish possess the feeding habits (described in Table 4)
that meet the biological considerations for wastewater purifi-
12
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cation; but, the most important consideration is their hardi-
ness and adaptability to a wide range of environmental
conditions (References 38 and 39).
Invertebrates
A variety of animal organisms that feed directly on
phytoplankton cultured in ponds receiving wastewaters has been
studied in an effort to develop a biological method for the
clarification and purification of these waste effluents
(Reference 10). Those organisms evaluated include Daphnia and
related species (water fleas), Artemla (brine shrimp), and
assorted bivalve mollusks (oysters, clams, and mussels).
The environmental parameters considered in the selection
of fish species for wastewater aquaculture treatment systems
are also applicable to invertebrate species.
Integrated Systems
Experimental systems that combine several types of
organisms rather than focusing on one or two types of organisms
for treatment or utilization of wastewater are referred to as
integrated systems (Reference 10). These treatment systems
derived from aquaculture concepts may either contain more than
one active component in a single unit or a combination of
aquaculture components to form a process. Such systems are
highly structured and often display complex food chain inter-
'relationships.
Culture Basins
Culture basin size, number, and configuration are
determined by the degree of pretreatment of the influent and
also the discharge requirements of the effluent. The following
characteristics of an optimal aquatic plant culture basin are
based upon current experience with experimental systems in
operation and upon recommendations by Dinges (Reference 41) and
Wclverton (Reference 42). An engineering design manual
recently made available by Gee and Jenson Engineers outlined
the factors to be considered and evaluated in constructing a
water hyacinth treatment system (Reference 43). Most aquatic
animal-based systems studied have used existing lagoons, and
hence, specifics on optimum number, size, and configuration of
culture basins have not been established (Reference 15).
The majority of aquatic plant systems studied to date have
been designed to operate with three basins in series. Single
cell stabilization ponds, however, with water hyacinth coverage
have been employed successfully. If the objective is the
control of algae in the effluent from a wastewater
14
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stabilization pond, then a single basin appears to work just ae
effectively as the series arrangement. A minimum of two
separate ponds, each having a capacity to treat the average
daily flow, has been recommended. Such a dual aquatic plant
system would allow for periodic cleaning and maintenance
without any interruption of treatment.
By their very nature, animal-based and integrated
aguaculture systems require multiple basins, and the optimum
number of basins to be used is dependent on individual circuo-
stances. Specific reasons for the use of multiple cells would
include among others, the need to regulate food chain relation-
ships, maintain proper culture population, and control the
level of dissolved oxygen (Reference 15). In addition, these
systems should be designed to allow maximum operational flexi-
bility and uninterrupted services when any basin must be taken
cut of operation for cleaning or other maintenance purposes.
The most critical design factors for water hyacinth basins
noted by Dinges were the rate of flow of wastewater through the
basin and uniform distribution of wastewater at inlet and
outlet zones (Reference 41). Thus, broad rectangular basins
having a length to width ratio of at least 3:1 have been recom-
mended. This configuration minimizes short-circuiting, wind
effects, and eliminates variations in treatment efficiency.
Individual basin size, width, and depth, are set allowing
for efficient harvesting and routine maintenance. A maximum
basin width from 15.2m (50 ft.) to 30.4m (100 ft.), -with a
minimum of 7.6m (25 ft.) , is recommended, dependent on the type
of harvesting equipment available. Individual basin size of a
maximum of 0.4ha (1 acre) has also been recommended. Mean
basin depths have varied from 0.38m (1.25 ft.) to 1.83m (6 ft.)
with a depth of 0.91m (3 ft.) or less recommended. A critical
concern is to provide adequate depth for the development of the
floating plant/root system. Systems designed for nutrient
removal have used a depth of approximately 0.4m (1.25 ft.) to
ensure complete contact of the wastewater with the root system
(Reference 16) .
Culture basins are constructed by excavating and diking
the required area. Berms designed for easy maintenance and
harvesting should have a top width of 3m (10 feet), and sides
with a vertical to horizontal slope of 1:3. The berms are
compacted to prevent seepage or keyed into an impervious soil
layer if leakage through a sandy topsoil is expected. Minimum
freeboard above the design water level should be at least two
feet. In areas with a high groundwater table, it may be
necessary to seal the pond bottom. This can be accomplished
with clay, cements, plastic liners, or asphalt. A slope of at
least 0.5 percent from the upper end to lower end of the basin,
& ,
15
-------
and a sump excavated at the lower end, would facilitate rapid
drainages.
Inlet and outlet structures and piping in each pond should
be designed to distribute flow evenly across the pond. For
small basins, a single inlet and outlet centered on the short
sides of the basins is suitable. In larger ponds, multiple
inlets, such as perforated pipes, and outlets or continuous
weirs have been recommended. Inter-connecting piping between
ponds would provide maximum operation flexibility and allow
parallel or series operation. All piping should be valved and
drains provided in each pond. A fixed barrier of screening, or
a crushed rock or gravel dike around the outlet can serve to
retain the plants, allow for reaeration, and prevent the dis-
charge of plant debris.
Supplemental mechanical aeration, such as surface
aerators, have been used in aquatic plant basins. Submerged
aeration lines, consisting of lead-weighted valved polyethylene
tubing, have been used in both aquatic plant and fish culture
basins.
COMMON PROCESS MODIFICATIONS
Common process modifications include the following:
o Basin Size and Configuration: Variation may occur
when land to be used is odd-shaped or when
an existing lagoon system is to be redesigned.
o System Enclosures: Greenhouse-type protective covers
allow the extension of aquatic plant systems to cli-
matic zones where plants cannot exist naturally or
where plant growth is seasonal.
o Beating Basin Waters: Sources of heat which might be
used to warm culture basin waters could include
methane produced from harvested biomass, cooling
waters, solar panels or refuse incineration
(Reference 41).
o Chemical Removal of Phosphorus: The addition of
alum, ferric chloride, or other chemicals can remove
phosphorus remaining in the effluent from tertiary
aquatic plant systems.
o The aquatic plant treatment process may also be
suited for seasonal use in treating wastewaters from
recreational facilities and those generated from
processing of agricultural products* Other potential
uses night include renovation of small lakes and
16
-------
reservoirs, pretreatment of surface waters used for
domestic supply, storm water treatment, deminerali-
zation of water, recycling fish culture waters, and
biomonitoring purposes (Reference 41).
17
••*+•
-------
SECTION 2
RECOMMENDATIONS
The use and reliability of aquaculture processes in waste-
water treatment system should increase as successful
experience is gained in the future. Costs are expected to
become more competitive with conventional treatment systems as
aquaculture systems become optimised. Based on this assess-
ment* the following recommendations are made regarding the
implementation of aquaculture systems for wastewater treatment:
O Construction and Pasign of Aquaculturg Baaing.
Various methods of basin construction should be
studied to determine the most cost-effective methods.
The design of the basins should be optimized to
minimize energy requirements'and facilitate minimum
maintenance of the basins.
O Eng}n»»rinp Pgaipn Criteria. Research projects
should be developed to test design criteria (i.e.,
surface and organic loadings). This information is
necessary for the design of various types of aqua-
culture system.
' o Labor Baqtiir»«»nfe«. Available information regarding
O&M labor requirements is limited. Operating
facilities should document actual labor requirements
to enable other agencies to accurately estimate labor
demands and review operational procedures.
o £fiALt. Accurate documentation of the construction
and O&M expenses should be maintained by operating
facilities. This information would be helpful for
future cost estimates. Existing documentation of
costs is poor.
O Suitability of Specific Symtmmm ^o Geographical Ba-
flifini. A guide should be developed to identify geo-
graphical regions best suited for various aquaculture
system types and plant and animal species.
o performance Pata. Performance data for BOD, SS, ni-
trogen, phosphorus and coliform have been collected
<*
$
•4
•*.
f
fc
-------
and published foe son* of the full seal* facilities,
but this should also have been done for all of the
full scalt facilities. Additional parameters that
also should be nonitored are total solids, dissolved
solids, suspended solids, COD, heavy metals,
refractory organics, and pathogens.
information Transfer.' Publication of successful
project information in widely read professional
publications is needed to inform wastewater agencies
of aguaculture wastewater treatment opportunities.
Guidance documents published by EPA for distribution
by state and regional regulatory and funding agencies
to wastewater management agencies would be useful in
promoting aguaculture technology. Currently, many
state and regional agencies are not well informed
regarding the application of aguaculture technology.
Research and Development Magda. Water hyacinths have
emerged as the primary aguaculture mode due to the
historical interest and development of this
technology by aguatic biologists. Alternative
systems (e.g. other plant species) have not received
similar attention and, therefore, are not at the same
level of development. Research and development of
alternative plant systems that overcome the con-
straints of water hyacinths are needed to spur more
widespread use of aguaculture systems for wastewater
treatment.
19
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SECTION 3
DEVELOPMENTAL STATUS OF AQUACDLTURE SYSTEMS
SUMMARY OF RESEARCH FINDINGS
The developmental status of each of the four specific
aguacultuce systems (aquatic macrophytes, invertebrates, fish
and integrated systems) are presented individually.
Summary of Research Findings —
The status of water hyacinths in wastewater treatment has
progressively developed during the past few years of research.
Water hyacinths have been extensively studied at the laboratory
level and tested at the pilot scale level. Continuation of
these efforts has produced a number of full-scale experimental
and demonstration systems for treating primary effluent, for
upgrading existing systems, for advanced secondary treatment,
and for full advanced wastewater treatment.
Hastewater treatment experience with duckweeds has not
been as extensive. Research with other aquatic plants has been
limited.
Bench Seal* Research —
Based on theoretical projections from observed plant
nutrient content and potential productivity, water hyacinths
were suggested as excellent candidates for nutrient removal
systems by several researchers. Boyd calculated that 1,980
kg/ha of nitrogen and 322 kg/ha of phosphorus could be removed
per year by a continual culture of water hyacinths (Reference
23). Steward estimated that 0.4 ha (1 acre) of water hyacinths
could potentially utilize all of the nitrogen fraction con-
tained in the secondary treated wastewater of 130 to 595 people
with corresponding growth rates estimated at 6 to 27 dry metric
tons/ha/yr (Reference 44). At the same estimated growth rates,
the phosphorus production of 40 to 180 people could be used.
These nutrient removal potentials were based on the yearly per
capita contributions of 4kg (9 Ibs.) K, and 1.4 kg (3 Ibs.) P.
Projections of this nature were further substantiated in
actual nutrient removal studies. A variety of laboratory
20
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experiments were designed to determine the absorption of
nitrogen and phosphorus by water hyacinths. Rogers and Davies
studied the changes in nitrogen and phosphorus concentrations
in batch and continuous flow cultures containing a single water
hyacinth plant (Reference 45). Based on their findings and
estimates of annual domestic wastes per capita of 3.2 kg K and
0.9 kg P, they.projected that 1 ha of water hyacinths (approxi-
mately 1.62x10* plants) could uptake an amount of nitrogen and
phosphorus equivalent to the wastewater from over 800 persons.
An 86 percent reduction of phorphorus from an initial concen-
tration of 1.4 mg/1 to 0.2 mg/1 by water hyacinths grown in
sewage effluent under batch conditions for a five-week period
was noted by Ornes and Button (Reference 46). In another
study, Sheffield found that a laboratory scale system, con-
sisting of a water hyacinth pond followed by an air stripping
and coagulation unit receiving 8.0 liters/day of secondary
treated wastewater, could reduce ortho-phosphates to 0.7 mg/1,
nitrate nitrogen to 0.2 mg/1, and ammonium nitrogen to 0.1 mg/1
from initial concentrations of 60, 10, and 23 mg/1,
respectively (Reference 47). Scarsbrook and Davis reported
that water hyacinths absorbed 2.87g of phosphorus, 6.93g of
nitrogen, and 8.73g of potassium during a 23-week period batch
study when grown in sewage effluent contained in pools 2.7m in
diameter and 0.7m in depth (Reference 48).
Laboratory investigations on the pollution removal
capabilities of water hyacinths were conducted by Wolverton
(reference 49). Table 5 summarizes the reductions in waste-
water .constituents in 5-liter cylinders containing hyacinths
and domestic sewage. Alligator weeds were also tested under
the same conditions and demonstrated ability to remove
nutrients and pollutants from domestic wastewater.
Recent laboratory experiments by Holverton were conducted
to correlate BOD5 removal with known wet masses of water
hyacinths (Reference 42). Data from these experiments using
domestic wastewater indicated that an average total BOD5
removal rate of 4.0 mg BOD5/gram wet weight of hyacinths could
be achieved with a seven-day retention time.
The ability of water hyacinths to remove chemical and
metal pollutants has also been documented under laboratory
conditions (reference 51, 52, 53, 54 and 55). Table 6
summarizes these capabilities.
21
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TABLE 5. PERCENT REDUCTIONS XH WASTEWATER CONSTITUENTS UTILIZING WATER
OUR BATCH LABORATORY CODZXICNS (Reference 49, 50)
Raw Sewage
Secondary Effluent
7-Day Exposure 7-Day Exposure
14-Day Exposure
Measurements W/Plants Control W/Plants Control W/Plants Control
Total Kjedahl
Nitrogen
Total
Phosphorus
Total Suspended
Solids
BODj
92
60
—
97
18
13
—
61
75
87
75
77
13
11
15
6
89
99
77
—
15
25
12
—
TABLE 6. CAPABILITY OF WATER HYACINTHS TO REMOVE VARIOUS
CHEMICAL AND METAL POLLUTANTS PROM WATERS
(References 51, 52, 53, 54 and 55)
Chemical
and Metal
Pollutants
Cadmium
Cobalt
Lead
Mercury
Nickel
Silver
Strontium
Phenols
lARORATORy ^XPERIMEKfS
mg of Pollutant Removal
per gram of Dry Plant
Material per day
0.67
0.57
0.18
0.15
0.50
0.65
0.54
36
FIELD POTENTIAL
kg of Pollutant
Removed/acre/day*
0.161
0.137
0.042
0.036
0.120
0.156
0.130
8.640
*Based on removal of mature plants every 24 hours.
-------
Duckweeds have been investigated less extensively than
water hyacinths under laboratory conditions. Harvey and Fox
reported that Lcarna minor removed substantial amounts (86
percent and 67 percent) of total kjeldahl nitrogen and total
phosphorus from 22 liters of secondary wastewater effluent for
a 10-day test period (Reference 56). Sutton and Ornes obtained
over a 90 percent reduction in the phosphorus content of sewage
effluent over an eight-week growth period using a mixed
population of Lemna spp. (Reference 57) in a batch system.
The same investigators, using spirodcla poiyrhiaa. reported &
reduction from 3.53 ug/1 to 0.09 ug/1, representing a 97
percent decrease in the phosphorus content of secondarily
treated wastewater effluent studied in batch conditions during
a 12-week test period (Reference 58).
A laboratory investigation to determine the wastewater
treatment effectiveness of a variety of aquatic macrophytes has
been initiated by EPA's R.S. Kerr Environmental Research
Laboratory (personal communication with Dr. W.R. Duffer,
principal investigator). Batch screening tests have been
conducted with six species of aquatic plants utilizing primary
and secondary effluents. Bench scale flow tests for species
having best survival and showing most promise for removal of
pollutants were undertaken in 1981.
Pilot Scale Research—
The ability of water hyacinths to remove BODr, suspended
solids, and other pollutants as well as inorganic nutrients
from wastewaters has been reported in pilot-scale studies by
numerous investigators. Systems providing both secondary and
advanced wastewater treatment have been studied. In 1965,
Purman and Gilcreas reported reductions of approximately 75
percent in organic and ammonia nitrogen by water hyacinths
grown in the third cell of a four-celled' raw wastewater
oxidation pond having detention time of five days (Reference
59). The plant-covered cell had an area of 0.2 ha (0.5 acre)
and averaged 1.07m (3.5 ft.) in depth. Clock reported that, at
a detention time of five days, nitrates were reduced 75 percent
and phosphates were reduced 61 percent when secondary waste-
water effluent was in contact with a dense mat of growing
hyacinths (Reference 60).
In 1969, Sheffield and Furman studied nutrient removal in
secondary wastewater effluent passed through a hyacinth pond
and reported removals of 92 percent of nitrate, 35 percent of
ammonia, and approximately 50 percent of orthophosphates
(Reference 61). Minor, using hyacinth ponds to treat swine
manure, reported that the plants removed 10.4 kg (23 Ibs) of
ammonia nitrogen, 11.4 kg (25 Ibs) of Kjeldahl nitrogen, and
7.72 kg (17 Ibs) of phosphates per acre (0.405 ha) with a 102-
day detention time in ponds 46 cm (18 in.) deep (Reference 62).
23
-------
Neuse observed BOD5 reductions of 67 percent and total
suspended solids reductions of 79 percent in a study conducted
with stabilization pond effluent (Reference 63).
More recent and extensive pilot studies were conducted by
a group of scientists and engineers at the university of
Florida at Gainesville; the Texas Department of Health
Resources in Austin; and the National Aeronautics and Space
Administration (NASA) at the National Space Technology
Laboratories in Bay St. Louis, Mississippi. Results from the
water hyacinth system studied by these investigators are
discussed further, along with a single study involving
duckweed.
A three-phase water hyacinth study was carried out between
1971 and 1974 at the University of Florida at Gainsville
(Reference 64). The third cell of a polishing pond system with
a total surface area of 2,323 sq m (25,000 sg ft.) and an
average depth of 1.4m (4.5 ft.) was used for the first two
phases of the study. Receiving secondary effluent from a
treatment facility on campus, the flow into the test pond was
approximately 1900 cu m/d (0.5 mgd) with a surface loading rate
of 0.25 cu m/sq in/day (3.70 acres/mgd). The detention times
were varied from 6 to 24 hours to observe their effects on
nutrient removal. Nutrient removal was below desired levels at
the low detention times and large depths tested, but results cf
the study indicated that both detention time and depths were
important in nutrient removal by water hyacinths. Therefore,
in the third phase of the study three 9.3 sq m (100 ft.) ponds
were constructed with depths of 0.34, 0.64, and 0.70 m (1.1,
2.1 and 2.3 ft.) to evaluate the effects of varying depths and
detention times.
Nutrient reduction rates from this third -stage were
significantly higher than those observed in the first two
phases of the study. Results of Phase 3 studies are summarized
in Table 7. Surface loading rates for any specific pond depth
were directly related to nutrient removal rates.
A two-phase study was initiated in June, 1975, at the
Williamson Creek Kastewater Treatment Facility in Austin, Texas
(References 65 and 66). The City of Austin provided an experi-
mental hyacinth culture basin, 9.1 m (30 ft.) in width and 64 m
(210 ft.) in length, and divided into four sections by crushed
stone barriers. Secondary wastewater inflow to the system was
maintained at 109 cu m/day (28,800 gpd) for both study phases.
Surface organic loading was 43.4 kg/ha/day of BOD5 (38.7 Ibs/
acre/day) during the first phase. Mean water depth was 1 meter
(3.3 ft.) and theoretical system detention time was 5.3 days
fox the first phase. Water with a surface organic loading of
24
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TABLE 7. SUMMARY OF NUTRIENT DATA FROM TBREE TEST PONDS
DURING PHASE 3 OF THE PILOT STUDIES AT THE
UNIVERSITY OF FLORIDA FROM JULY, 1973 TO JUNE, 1974
(Reference 64)
Nutrient
Total
Phosphorus
as P
Total
Nitrogen
as N
Average
Influent
Value
(mg/1)
3.44
13.86
Average Effluent
Detention
Time
(hours)
12
24
48
96
12
24
48
96
Concentrations
0.34 m
Pond
3.42
2.86
1.82
--
12.05
5.89
2.72
— •
0.67 m
Pond
3.55
3.08
2.30
—
12.48
7.95
4.98
~
(mg/1)
0.70 in
Pond
MM
3.33
2.90
1.95
—
11.49
6.85
3.09
8.93 g/sq si/day of BOD5(79.7 Ibs/acre/day) was used in the
second phase. Mean water depth was 0.85 m (2.8 ft.) and
detention tine was 4.5 days for Phase 2.
Table 8 presents the water quality data obtained from this
pilot study. The standing crop of hyacinths at the end of the
growing study phase represented a dry weight biomass production
of 3,184 g/cu m.
NASA has been using higher aquatic plants to upgrade
domestic wastewater treatment lagoons and treat chemical
wastewaters for the past seven years (Reference 22). studies
have also been conducted in using aquatic plants to recycle
waste in future space stations (Reference 67). In addition to
upgrading all wa&tewater treatment systems at the National
Space Technology Laboratories (NSTL) by using water hyacinths
and duckweeds, NASA has conducted several field studies with
local communities in southern Mississippi (Reference 42).
Water hyacinths were introduced into a single cell lagoon
at NSTL in June, 1976 (Reference 68). Receiving a relatively
light load (TSS 112 mg/1, BODe 79 mg/1), the facultative lagoon
served a population of 2,000". Background data revealed that
the existing lagoon did not meet secondary standards set for
BOD5 and suspended solids. Results during a 14-month hyacinth
covered study period showed that the operation of the system
was improved when hyacinths assumed a primary role. Another
25
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TABLE 8. SUMMARY OF AVERAGE WATER QUALITY PARAMETERS AFFECTED |;
BY WATER HYACINTH TREATMENT IN PILOT STUDIES AT |
WILLIAMSON CREEK, TEXAS (References 65 and 66) |[ •
"*-' L_»—^^—- ~ — -" ' .•^•••^^•^••^^•^••^^••^^•^•^••^^^^M^^*"—•^^•^^•^^™^»»»»»^"»*^^"^^"^*«"^""*"^^™"^^^^^^" ^
First Study Phase Second Study Phase ;;|
June 1975 - February 1976 May 1976 - August 1976
Influent Effluent % Reduction Influent Effluent % Reduction li
BCX>5, mg/1
TSS, mg/1
TN, rog/1
TP, rog/1
Fecal '
Colifonn
Bacteria/
100 ml
22.6
43.3
8.2
5.6
2,895
5.2
7
2.5
4.4
31
77
84
69
21
—
46.5
117
9.9
6.9
27,423
5.7
7.5
3.6
5.8
363
87
93
63
15
—
one-cell facultative lagoon located at Lucedale, Mississippi,
was studied extensively with and without water hyacinth
coverage (Reference 69). Again, the most significant overall
improvement in the effluent quality occurred with complete
overage of hyacinths. A complex lagoon system at Orange
rove, Mississippi, was used for conducting a 12-month study
with water hyacinths in effluent from aerated lagoons
(Reference 22).
A pilot scale duckweed study is being conducted using a
two-cell lagoon system located at Cedar Lake development in
North Biloxi, Mississippi (Reference 42). Duckweed coverage of
the second, unaerated cell occurred through natural means and
NSTL began monitoring the system in April, 1979. Design
characteristics and performance data for this system and the
water hyacinth pond systems studied by NASA/NSTL are summarized
in Table 9.
Aerobic ponds populated principally by submerged aquatic
plants (PjB±AJD£S£ifiji £c.ljLo..&jLfi, £Llfide_fi panadensls., and
Ceratophyllum demersum) were evaluated as part of a field-scale
research facility at Michigan State Universtiy, East Lansing,
to define wastewater processing limits imposed by ecological
mechanisms in both aquatic and terrestrial systems (Reference
70). A series of four ponds ranging from 3 to 5 ha (1.2 to 2
acres) with a total surface area of 16 ha (40 acre) and a mean
26
I
-------
TABLE 9. SUMMARY OP DESIGN AND PERFORMANCE CHARACTERISTICS OF THE FILCT
WASTEWATER TREATMENT SYSTEMS DSING AQUATIC PLANTS STUDIED B1
NASA/NSTL (Reference* 16, 22, 42, 68, 69)
lfm¥ir*n
Criteria National Space
Technology Lab.
Types of Pre-
treatment
Flow
cu in/day
Surface Area
ha
Depth
on
Hydraulic
Loading
cu n/ha
Hydraulic Residence
Tire/Days
Organic
Loading
kg/he/day
Plant Cover
Percent
BGDe, ng/1
Influent
Effluent
T5S, ng/1
Influent
Effluent
Dissolved
Oxygen, ng/1
Sanpiing
Period
None
475
(0.125 ngd)
2
(5 acres)
122
(4 feet)
240
(25,660 gal/
acre)
54
26
(23 lb/acre/
day)
Hyacinth
100
110
57
97
10
2.3
6/76-9/77
Lucedale, Q
Mississippi 1
None .
937
(0.247 ngd)
3.6
(9 acres)
173
(5.7 feet)
260*
(27,800 gal/
acre)
67*
44
(39 lb/acre/
day)
Hyacinth
100
52
23
77
6
0
Odors at night
7-11/76
7-11-77
7-11/78
range Grove,
Eissi&siroi
2 Aerated
Lagoons
1000
(0.264 ngd)
0.28
(0.69 acre)
183
(6 feet)
3570
(381,670 gal/
acre)
6.8
179
(160 lb/acre
day)
Hyacinth
100
50
14
49
15
2.1
8/75-7/76
Cedar Lake,
Mississippi
1 Aerated
Cell
49
(0.013 ngd)
0.07
(0.17 acre)
150
(5 feet)
700
(74,840 gal/
acre)
22
•31
(28 lb/acre/
day)
Duckweed
100
35
15
155
14
0.5
5/79-11/79
27
-------
operating depth of 1.8 m (6 ft.) comprised the aquatic system.
The facility operated on secondary wastewater effluent at flow
rates ranging from 1,892 cu in/day (0.5 mgd) to 3,785 cu m/day
(1.0 mgd). Kith controlled harvesting, removals of 20 to 25
percent of the phosphorus input and 50 to 70 percent of the
total nitrogen input were estimated at a detention time of 28
days (Reference 71). Increasing the detention time to 120 days
reduced the incoming nitrogen values of 15 to 20 mg/1 to levels
as low as 0.01 mg/1 with only a small effect on the efficiency
of phosphorus removal.
The City of Roseville, California is the site of a pilot
study determining the effectiveness of nutrient removals by a
variety of aquatic macrophytes (personal communication, Dewante
and Stowell Engineers, Sacramento, CA). Preliminary culture
experiments tested water hyacinth, duckweed, water primrose,
cattail and bullrush in 8 m (25 ft.) trenches receiving
secondary wastewater effluent at varying detention tiroes.
Water hyacinths were selected for the pilot study which was
initiated in 1981. Additional research includes quantifying
bacterial populations associated with the aquatic plant roots.
The City of San Diego's 3,785 cu m/day (1 mgd) three year
demonstration project is under design .to test the feasibility
of using water hyacinths for the treatment of raw sewage. The
Water Utilities Department's plan could ultimately serve the
City's 0.45x10° cu m/day (120 mgd) of sewage through a network
of tanks and ponds over several hundred acres.
Full-Scale Facilities/Aquaculture Fact Sheets—
The municipal water hyacinth treatment systems listed
below are considered to be experimental at the present stage of
their development. These full-scale facilities are currently-
being monitored to learn more about system design and perfor-
mance and to develop operation and management procedures.
o Coral Springs, Florida: Tertiary treatment with
flows of 378 cu m/day (0.1 mgd).
c Lakeland, Florida: Advanced wastewater treatment of
secondary effluent with flows of 454-977 cu m/day
(0.12-0.26 mgd)
o Walt Disney World, Lake Buena Vista, Florida:
Both secondary and tertiary treatment with flows of
189 cu m/day (0.05 mgd).
o Williamson Creek, Austin, Texas: Advanced secondary
treatment with minimum flows of 1,325 cu m/day (0.35
mgd).
28
-------
o Hornsby Bend, Austin, Texas: Secondary treatment
with flows of 6,050 cu in/day (1.6 mgd).
o San Juan, Texas: Secondary treatment with flows of
1,514 cu in/day (0.4 rogd).
o Alamo, Texas: Tertiary treatment with flows of 1,514
cu in/day (0.4 mgd). i
i
o San Benito, Texas: Advanced secondary treatment with
flows of 2,460 cu m/day (0.65 mgd).
o Rio Hondo, Texas: Primary treatment with flows of
454 cu m/day (0.12 mgd).
Technical descriptions, process flow diagrams, and key
design and performance data for each of these systems are
presented in the following fact sheets.
29
-------
OffBUOD BTi Good springe
A large acala field
Florid*
Diatrict
using
plant
hyacinth! to
aince Hay*
•
UTS.
(B*feranc* 43, 72)
plant
to an advanced waatewetar treetaent plant baa bean uHHarway aince Hay, !**•• Beees on tbe
by tbe Onivaraity of florid* the facility waa daalgnad by Gee and Janaan Engineer*. Mater Quality
[•raeaHii of priaary concern are total nitrogen and total phoapbocua. Monthly data baa indicated
tbat decreeaing aurface loading ratea reenlted in increasing nutrient reaoval. Partner
inveatigation ia underway to deteraine if tbe influent »»P ratio can ba increeeed by aaaonia
feo allow ftrr
Activatad alndgt.
Surface Baain
Plow Area Deptb
ca a/day ba ca
(agd) (acre) (ft)
Surface lydraulic
Loading Detention
cu a>/ba/day Tiaw
(acre/agd) (d«ya)
Organic •uatrer Percent
Loading of Plant
(kg/ba/day) Baaina Cover
Averages
379
10.11
Total
O.S
(1.2S)
3§
(1.2S)
Averaget
11.7
(10.1)
fond At
31
100
POtFOUUI
DAtAt
BOD.
(ag/I)
TSS
(ag/1)
Nitrogen
(ag/1)
Pboapborua
(ag/1)
Xnflneat
Effluent
13.1
2.M
T7
S.«4
2.95
22.4
1.0
11.0
3.«
C7
•D DISPOSAL or BIOMASSs Periodic barveeting ia naceaaaxy to prevent leaf cnloroaia
> by overcrowding, •arveating 15 to 20 ftmf/L of the planta on a faor-waek cycle baa produced
nreeolta. Narveeted biomaae avaragea 137^ en a (ISO cu yd) and after a two to three week
drying period ia being coapoeted. ajopthly barveeting of tbe hyecintba requiree < to 7 boura and
- - iflf •' " ' ' " "
of tba
were about 91(5,000.
30
-------
QNQSjKBB FACT SBEET
PACtUR MO LOCmCMi *•>»]••»*,.
Wi City at Lakeland and talk County, Fieri*
(Reference 73)
DBKKXPTXOHs A demonstration project designed by Dawkina t Associates, Inc. was implemented in
January, 197*. Ihe capability of water hyacinth* is being investigated for the removal and recovery
of natrienta from secondary effluent prior to discharge, tte system »uat meet atringant nutrient
removal raqoinmanta tL5 mg/l Vt 0.4 ug/l 0) and ia further being grooved to becoae part of a
regional faeilitiea plan with an axpanaioa aa large aa 49*200 cu */day (13 agd) poaaible. The
waa designed with flexibility ia •anlpilating fltrthtf pollutant and hydraulic lf?aiHf*ot> and
FUMDX1IGMN
•end Me. t
Peed He. 1
Weir
Surface
Plow Area Basin
cu a/day ha Depth
(mgd) (acre) (cm)
Hydraulic
Surface Detention
Loading Time
(cu m/ha/day) (daya)
Organic Number Percent
Loading of Plant
(kg/ba/day) Baaina Cover
454-977 0.4 ha
(0.120- as
0.0251) (1)
dna
dna
dna
Partial
dna • data not available.
PEXPOPJIARCE DAYA
•00,
T8S
Nitrogen
Phosphorus
Influent (ag/l) t-32
Effluent (ag/l) 3-4
L _ 50-90
4-36
0-7
ID-LOO
f.7-27.3
1.0- 4.2
75-M
3.0-5.0
1.1-3.1
31-40
AW DXOOML OP BtDNMSi Three hamsstsd chsnmla intended to ancommodata a
or aqua-guard self-cleaning bar screen were included aa part of the design. Processing
considerations of the harvested plants include ch ' ~ ~ '
alletizi
id plants in
lahorattwy
Preliminary lahorattwy taste indicated that the pel
the feed option and market potential wiU be further
ipping, pressing* and drying aa part of a feed
tested that the pellet iasd feed ia suitable for
for the
« the water yality and flow date and productivity rates*
MS projected for the summer study
s nutrient and water
31
-------
AQUMXLXURE DM* SHEET
FAOLm MD UOffXCNi Halt Disney World, Florida
GRUOD Kf: Ready CrMk Utilities Company «d NED Enterprises
(Reference 74, 75)
DESCRIPTIONS The ability of water hyacinth* to provide both Mcondary and tertiary wastewater
treatment is fating demonstrated by NWa Experimental Prototype Community of Tommorrow OEPUOD. A
variety of modes of operation are provided by the bydraulically inter-connected concrete channel*.
A preliminary operation phase waa started in June* 1979, with primary effluent being poped into the
channels. Results indicated that the shallower depth of 38 cm (15 inches) was more effective.
Future operations include testing the hyacinths as a tertiary system, evaluating the ef tect of a
protective cover during winter Booths, and determing the amount of energy consumed in the system.
PROCESS FLOW DZAGRMI
or Tertiary
IMuent
Chaimeia
(HyeeMh iaefcie Shewn to »ereael Flow System Mode)
DBSatOUSBUA
Flow
cu m/day
(mgd)
189
(0.05)
Surface
Area
ha
(acre)
0.1
(0.25)
Basin
Depth Surface
cm Loading
(ft) cu m/ha/day
Varies
38,61,91 dna
(1.2,2,3)
Hydraulic
Detention
Time
(days)
5-14
Organic
Loading
(kg/ha/day)
dna
Number
of
Basins
3
Percent
Plant
Cover
100
dna • data not available.
PBRFOMAKE DATA!
July - Atiquat. 187 9
BOD5 TS8
1979-April 19BO
B005
TSS
Influent (mg/1) 300 200 dna dna
Effluent (mg/1) 27.9 22.9 dna dna
% Reduction 91 89 85 82
BMtVESTZK AM) DISPOSAL Of BIONASSt Results have indicated that the constant removal of older
plants was more effective for treating wastewater. So far, maximum productivity recorded was 162
dry metric ton/hm/year. This productivity was recorded during the second week in March, 1980. The
harvesting pattern for maximum productivity has not yet been determined. Harvesting equipment in-
cludes a front end loader, double-belt conveyor chopper and a forage wagon. The harvested biomass
is composted utilizing a windrow-system. Extensive studies are funded for the bioconversion of
ter hyacinths and sewage sludge to methane gas by anaerobic digestion.
32
-------
AQUACUL1URE FACT
AM) IOCATIOH. Williamson Creek Facility, Austin, Texas
onuocD BY. aty «< Austin
(Reference 41)
Following tbt successful ocnelution of tht pilot studies, as discussed in tbt previous
•action, s full-sod* system was placed into operation in October, 1977. A stabilisation pond was
convtrtad into a hyacinth basin and is being operated as an integral wit of the facility to upgrade
fof secondary effluent*
PROCESS FLOW DIAGRAM
Treated
MyaoMti Culture Baast
•enter
' OF XVtOBir. Aeration basin, clarifer, two lagoons in series.
DESIGN OUTBUA
Flow
cu at/day
(mgd)
1325-1703
(0.35-
0.45)
Surface
Area
ha
(acre)
12
(3)
Basin
Depth
em
(ft)
70-130
(2.3-4.
Hydraulic
Surface Detention
Loading
cu B/ha/day
dna
3)
Time
(daya)
6-9
Organic
Loading
(kg/ha/day)
56-72
Number
of
Basins
1
Percent
Plant
Cover
100
dna » data not available
PERFORMANCE DATAi
(Unpublished Data)
Influent
Effluent
Percent Reduction
Oetqbfr 1977-AuaiiBt 1979 8*nt**h*r 1979->Moo«Bh*r 19SO
BOD5
•9/1
41.9
12
71
T8S
•9/1
40
S.0
71
Fecal
Coliform
1/100 ml
93 S0
302
BOD.
•9/1
20.2
C7*
T8S
•9/1
34.2
9.1
73
Fecal
Coliform
9/100 B!
13,019
132
BAKVESTXBB AMD DISPOSAL OF BZONASSi A single, annual harvest is being practiced in this system
during tht winter to remove dried plants and basin debris from the culture basin. Binges suggested
that continuous tiemeel Iny in small hyacinth secondary treatment systems would disrupt treatment
(Reference 41). The hyacinth basin was out of operation during the winter periods as plants were
frozen and in a state of decay.
33
I
sSF
-------
AQUACULTOB FACT SHEET
MO LOOOICNs Borosby-Bsnd Sludge Treatment Facility, Austin, Texas (Reference 41)
OPBUOZb BYl City Of Austin
DESdtlPTIONi Waste activated sludge fro* two wastewater treatment plants is transferred to the
Hornsby-Bsnd sludge pond System. A hyacinth cultur* buin w*§ pcovioM to trttt tte pond lystMi
ovwtlow in Nay, 1979. Arf •xptnsion of th« hyacinth «y«t«n ha* b««n apptovtd through EBA'c
oomtruction grants program Vrojtctad plan* indudt providing protectivt grMnhouM oov«r§ for tht
hyacinth huim (paraonal oomunication with Ray Dingts, Vnu Dtpartaant of Baalth).
1DOCESB FUHDUfflWM
Intol Mruotur*
Hyacinth Baahi
Advanced
Secondary
ffflueiM
Oirtfal
MBIT or UffUSSTi Influent is the supernatant fro* ponds holding waste activated sludge.
DKIQl GRUBtlA
Surface
Plow Area
cu m/day ha
(mgd) (acre)
Basin Hydraulic
Depth Surface Detention
on Loading Tine
(ft) cu «/ha/day (days)
Organic Dumber Percent
Loading of Plant
(kg/ha/day) Basins Cover
3937
(1.04)
1.4
(3.5)
Average dna Appro*. 3 dna 1
123
(4)
dna
dna • data not available
DATAl
(Unpublished Data)
October 1979 - September 1910
BOD. TSS
•g/I mg/1
Influent
Iftlnent
• Mduction
51.2
21.9
45
96
43.7
53
•AKVEBTIIB AMD DISPOSAL OP BIOHASSi A single, annual harvest to remove dried plants and basin
ilrtrii from thy culture basin h** been followed.
34
-------
nB ttCt
noon MB uxmcMi m Juan,
ORRJOED BYi Rio Grand* Valley IbUatian Control Authority
(Reft
41)
TWO hyacinth culture basins were added to the Can Juan treatment facility to assist
tHe overloaded stabilisation pond systei. In addition, during short period*, canning operations
load the panda at 20 times the aeon* that is nonaeunfrfl Basin A has teen in operation and tested
at various depths and flow rates since July, 1171.
ILOH PMBBH
OBIT or nBSBMTi Aerated lagoon, stabilisation pond.
DESIGN OITBKIA
riow
cu B/day
(agd)
a. 170
(0.23)
b. 152
(0.22)
c. 1552
(0.41)
d. 1855
(0.4»
Area
ha
(acre)
each
pond is
0.1
(2.5)
Basin Hydraulic
Depth Surface Detention Organic lumber Percent
cm Loading Tine Loading of riant
(ft) cu B/ha/day (daya) (kg/ha/day) Basins Cover
61 7
(2)
^} dna " dna 2 dna
•1 <
(3)
137 7
(4.5)
dna • data not available
DATAi
¥••£ •••!!)£• far .tii1w»Hav 1171 fa
BOD*
Influent
a. »0
b. if
C. 2CC
d. 31f
Effluent
«
35
31
% Reduction
78 TSS
8> ag/1
87
00
Influent
a. Ill
h. 113
c. 222
d. 282
,r kB«4n a,
Effluent
30
11
30
32
% Reduction
73
•0
|(
"
D DUMSM, OF BJOMASIi A single annual harvest to
froi the cultura basin baa been followed.
tmon driec
and basin debris
35
-------
AQUACULTURE PACT SHEET
FK3LZR HO UJCATICHt Alamo, Unas
Wt Rio Grande Valley Pollution Control Authority
(Reference 41)
IWo hyacinth culture basins were'completad and planted with hyacinths in April, 1979.
ttT<«« were pl»c«l into operation to »upple»«nt the existing stabilization ponds in the treat-
•snt of aoBMtie «f fluent and canmry wastM.
PROCESS
DIAGRAM
Treated
Distributer
tarrier
Or XNRjOBfri Zahoff tank, trickling filter, aeration basin, two stabilisation ponds in
(Motes Limited preliminary data)
Surface Basin Rydraulic
flow Area Depth Surface Detention Organic Number Percent
cu m/day ha cm Loading Time Loading of Plant
(mgd) (acre) (ft) cu m/ha/day (days) (kg/ha/day) Basins Cover
1.35
(3.3)
l.OS
dna
dne
dna
dna*data not available
pjBUi Data not available.
AmO D.TCTOML Of BTQSMBi Data not available.
36
'•. . „ ./«>•' •»>.'" V-J -{v'i--"#-'« ,i^--.'».- -»toik - •
-------
na SHEET
PACILOT AH5 LOdOlCMt san Benito, Unas ttsference 41)
OPSUBED BYi City of SKI Benito
KSOlimOllt The last pond in a stabilization pond system was divided into three sections by
earthen dikM to Mcvt w an upwiMntal nyceiBth trMttMnt facility.
BOOBS ItGHOUOUW
HyaoMD taatae
•arrtor
1 Or OKOBHTi four •Ubiliiation pandi in MriM.
Surface Basin Hydraulic
Plow Area Depth Surface Detention
cu m/day ha cm Loading Time
(mgd) (acre) (ft) cu m/ba/day (days)
A. O.I
(2)
dna B. O.I dna dna dna
(2)
C. 2.0
(5)
Organic number Percent
Loading of Plant
(kg/ba/day) Basins Cover
0
dna 3 50
100
dna • data not available
DATA I
Inrll 1«7i-IUreh 1979
BOD.
TSS
Influent dna
Effluent (»g/l) 17
dna
35
HAXVBSTXNE AMD OISK6AL OP BIONASSt Changes in the design and operation of the system are being
considered alter termination of the experimental phase. Considerations include large circular
concrete hyacinth basins divided into ^ie-shapsd* sections (personal communication with lay Dinge*.
~ of Bssltfa).
37
-------
FACT
rACXLinr AND LOCATIONS Rio Hondo, Texas
BJfj The City oC Rio Bondo
Utterance 41)
Ht The City of Rio Bondo planted hyacinths in their raw sewage stabilization pond a few
years ago. Vend effluent quality improvement was noted but was hampered by the sludge deposition
accumulating since 1950. The stabilization pond was bypassed in 1978 and raw wastewater discharged
directly into constructed hyacinth culture basins.
IKXZSS FLOW DIAGRAM
flaw
Sewage
[
•t
Pump for Transfer
Maine
Effluent
Outlet
Hyacinth Basins
Or UffUJUJTi Mom
Surface Basin Bydraulic
Plow Area Depth Surface Detention
cu a/day ba ca Loading Tiae
(»gdl (acre) (ft) cu a/ha/day (days)
Organic Number Percent
Loading of Plant
(kg/ha/day) Basins Cover
454
(0.12)
0.41 ea
(1)
dna
dna
dna
Por Basin At
197
100
dna • data not available
PERFORMANCE DATAI
Julv 1971-IUv 1979
Influent
Effluent
BODS
dna
(ag/1) 16
TS8
dna
24
June 1979-M*rch 1980*
BOD5
dna
17
T8S
dna
18
•Unpublished data
HARVBBTXNS AMD DX8KBAL OP BIOMABSt there has been
dragline.
periodic removal of dried plants with a
COmtDRSi ihe dty has recently restored the raw sewage stabilization pond and placed it beck into
operation. Modifications were also asde to improve the distribution of wastewater through hyacinth
basins (personal communication with Ray Dinges).
38
-------
Invertebrates
.Bench Scale Research—-
An experimental system was designed for the controlled
'utrophication of wastewaters with a marine algae
TTetraselmis) and brine shrimp (References 78 and 79). In a
series of batch laboratory tests, Tetraselmis was cultured in
the first stage in beakers containing various dilutions of raw
and treated wastewaters to use as a food source for brine
shrimp (second stage) while water quality parameters were moni-
tored. Results from this two-stage process indicated that
there was a substantial drop in total suspended solids and
ammonia, little change in phosphates, nitrates and nitrites,
and an increase, in all cases, in BOD during the 72-hour test
periods. An algae stage was added after the brine shrimp to
allow for further reduction of the BOD values. Results from
the three-stage process (raw wastewater algae brine shrimp
algae) employing 250-ml containers under batch conditions are
summarized in Table 10. The experiment allowed for 24-hours
growth for each of the algae steps and 48 hours for brine
shrimp.
TABLE 10. SUMMARY OF WATER QUALITY PARAMETERS RESULTING FROM A
THREE-STAGE BATCH LABORATORY EXPERIMENT CULTURING A
MARINE ALGAE (TETRASELMIS) AND BRINE SHRIMP FOR 96
HOURS (References 78 and 79)
Parameter
k (mg/1)
BODj
TSS
NO-3
NO-2
NH3
FO 3-
P04
PH
Influent
(raw waste-
water)
318.0
120.0
30.0
0.02
0.30
20
7.0
Stage 1 Stage 2
(algae (brine shrurp
culture) culture)
5.5
45.0
14.5
0.01
0.10
16.5
8.8
23.0
20.0
7.0
0
0.75
10.0
8.7
Stage 3 % Reduction
(algae (influent to
culture) Stage 3)
4.5
3.5
1.0
0
0.02
4.8
8.7
98
97
97
100
93
76
—
A continuous flow system was incorporated into the
laboratory experiment to study the retention and survival of
pathogenic bacteria and viruses. A significant reduction in
-------
number of fecal coliforms and enterccocci on the passage of
sewage through the algae and brine shrimp culture tanks was
. rted. No enterococci end an insignificant number of coli-
orms (3.7 per brine shrimp) were isolated from tissue speci-
mens, which were assumed to be associated with the algae pre-
sent in the gut of the brine shrimp.
Pilot Scale Research—
An experimental pilot pond, provided by the City of
Giddings, Texas, and supplied with a portion of effluent fron, a
waste stabilization pond, was used to Bain tain a PaphtHa (vater
fj**i ccltore under contrclled conditions to upgrade secondary
effluent (References 80 and 81). Severe restrictions of
paphnia production in most pond systems are related to high pH
levels due to algae growth. Preliminary studies evaluated the
effectiveness of pB control by regulation of pond exposure to
sunlight, chemical addition/ and sulfide reduction through
mixing-aeration of pond waters. Sustained culture of Daphnia
at a high population level was found to be feasible. Water
quality parameters evaluated during two study phases of the
Daphnia culture unit are summarized in Table 11. Detention time
for both study phases was 11 days with a BODc loading rate of
39 to 49 kg BOD5/ha/day (35 to 44 Ibs. .BOD5/acre/day).
TABLE 11. SUMMARY OF WATER QUALITY PARAMETERS AFFECTED BY A
DAPHNIA CULTURE POND DURING A CONTROLLED OPERATION
PERIOD (References 80 and 81)
First Study Phase
Januar 1972 - March 1972
Parameter
Influent Effluent
Percent
Reduction
Second Study Phase
February 1973 - April 1973
Percent
Influent Effluent Reduction
BODc, mg/1 45.4
COD, mg/1 271.1
VSS, mg/1 77.2
Total Coliforms,
per 100 ml 32,680
Fecal Coliforms,
per 100 ml 6,880
14.2
90.6
10.8
9,160
84
69
67
86
72
99
57.5
158.5
78.4
—
. ^«^
11.8
70.0
13.0
•—
™
79
55
33
—
— •-"
Utilization of soluble nutrients and minerals were limited
in the Paphnjq culture unit. Phosphorus content of the
effluent was comparable to that of the influent. Nitrate and
organic-bound iron accumulated in the unit. Daphnia harvest
and potential usage as a protein additive to animal feeds was
considered. Based on experiences gained from the pilot pond
40
-------
operation, Dinges formulated zooplankton culture unit design
and operating features (Reference 82).
A similar two-stage Daphnia culture unit also designed to
upgrade secondary effluent was explored by the Las Virgenes
Municipal Water District, California, in 1973 (Reference 83).
The system consisted of a shallow algae culture pond followed
by a Daphnia culture pond. The system's reduction of COD was
reported to be above 40 percent. Nitrogen and phosphorus
removal efficiencies were hampered by occasional invasion of
Daphnia in the first-stage pond, which decimated the algal
population. Lack of success in controlling such events was the
principal obstacle to further development of the pilot system
(Reference 15).
Zifih
General Studies—
Numerous examples of fish culture operations with a
variety of species in wastewater stabilization ponds are noted
in the literature (Reference 84). In 1969, channel catfish
were stocked and raised successfully in a series of four
tertiary sewage treatment ponds located in Ames, Iowa
(Reference 85). The following year, fathead minnows were prop-
agated in the same ponds (Reference 86). The same fathead
minnow propagation in a municipal wastewater stabilization pond
was demonstrated by Trimberger in Michigan (Reference 87).
Recently, an investigation was conducted in Wisconsin to assess
the potential of wastewater treatment lagoons located in that
state as culture sites for fathead minnows (Reference 88). The
feasibility of developing a sport fishery in tertiary treated
wastewater was tested with channel catfish, Tilapia hybrids,
and rainbow trout (Salmo qairdneri) at the Tucson Sewage Treat-
ment Plant, Arizona (Reference 89). Although certain water
quality parameters, including dissolved oxygen, ammonia, ortho-
phosphate, BOD, turbidity and water temperature, were con-
sidered and monitored during these operations, analysis of
water quality improvement was limited as these systems were
orientated toward examining the suitability of lagoon effluents
for fish production.
A lagoon wastewater treatment system was used for rearing
muskellunge (££fix masguinonqy) to 23 to 25cm (9 to 10 in.) lake
planting size in Dorcester, Wisconsin (Reference 90). The
system consisted of two aerated lagoons, each 0.57 ha (1.4
acre), with an average depth of 3m (10 ft.). Minnows and 5,000
- 6cm (2.5 in.) long muskie fingerlings were stocked in the
following third pond, 0.2 ha (0.5 acre) and 3 m (10 ft) in
depth.
41
*
-------
At a flow of 241 cu in/day (63,600 gpd) and loading rate of
1C1 kg BODc/day (22 Ib BOD5/day), detention tines averaged 51
days for each of the first two lagoons and 26 days for the fish
culture unit. Monthly effluent quality data recorded from
January, 1976, to December, 1977 averaged about 6 ng/1 for both
BCDe and suspended solids and did not exceed 16 mg/1 during the
entire test period. Data for the fish culture unit alone was
not available, thus the extent to which the fish contributed to
the effluent quality improvement is not known. However,
experience with other aerated lagoon systems of this type
suggests that the fish culture pond may have served as a
polishing unit reducing BOD values and suspended solids in the
final effluent (Reference 15).
Pilot Scale Research—
Two pilot studies which evaluated the effect of fin fish
on water quality improvement were conducted by Coleman et al.
(References 40 and 91) at the Quail Creek Lagoon System in
Oklahoma City (1973) and by Henderson at the Benton Services
Center, Arkansas (1978-79) (Reference 39). Both studies
utilized six-cell (operated in series) lagoon systems to
treat raw wastewater. The first two cells were for wastewater
stabilization and plankton culture and the remaining four used
for the polyculture of fish. The Q.uail Creek system used
mechanical aeration for the initial stabilization step and
channel catfish as the major culture species. The system in
Arkansas accomplished initial wastewater stabilization without
supplemental aeration and used silver and bighead carp as the
major culture species. The design characteristics and perfor-
mance data for the last four cells of these two fish systems
are summarized in Table 12. All parameters are based on the
fish culture unit only.
Both systems performed satisfactorily in removing organics
and suspended solids and provided an advanced secondary
effluent. The secondary treatment standard for BOD5 of 30 mg/1
was met in the effluent from the second cell in the Quail Creek
System. The secondary standards for suspended solids (30 mg/1)
and fecal coliform (200/100 ml) were met in the effluent from
the fifth cell. In the Arkansas System, BOD5 and suspended
solids standards were met in the effluent of the first fish
cell. There were no reported incidents of fish kills, indi-
cating that the ammonia, nitrate, dissolved oxygen, and pH
levels (shown in Table 12) were within tolerable ranges for the
cultured fish species* As no supplemental feeding of fishes
occurred during both experiments, increase in fish biomasa was
dependent upon constituents present within the system. A food
habits study by Coleman et al. allowed general classification
of the fishes according to position in the food web.
42
-------
TABLE 12. SUMMARY OP DESIGN CHARACTERISTICS AND PERFORMANCE
DATA POR TWO PILOT STUDIES UTILIZING PISH POR
WASTEWATER TREATMENT (Reference 39, 40, 91)
Item
Design Criteria
Quail Creek Plant Benton Services Center
Oklahoma Arkansas
Method of influent
stabilization
Sampling period
Major fishes cultured
Minor fishes cultured
Flow, cu in/day
Surface area, ha
Depth, m
Detention tine, days
Organic loading rate
kg BODb/ha/dey
kg TSS/ha/day
Initial fish stocked
kg/ha
Net fish production
kg/ha/no
Mechanical aeration
6-73 to 10-73
Channel catfish
Tilapia
Minnows
3785 (1.0 ngd)
64 (26 acres)
3-3.6 (10-12 ft.)
Not available
Not available
29 (26 Ib/acre)
44 (39 Ib/acre/nc)
Dnaerated stabilization
ponds
12-78 to 7-79
Silver and Bighead Carp
Channel catfish
Buffalofish
Grass carp
1,711 (0.45 mgd)
6.5 (16 acres)
1.25 (4 ft.)
48
43.5 (38.8 Ib/ac/day)
20.4 (18.2 Ib/ac/day)
426 (380 Ib/acre)
417 (390 lb/acre/no)
Performance Data
Arlcamms
Wastewater %
Bararceter Influent* Effluent** Reduction Influent* Effluent**
BCDj, mg/1
TSS, mg/1
Total N, mg/1
NB3-N, mg/1
NDj-N, mg/1
NGv-N, mg/1
Tctal P, mg/1
Fecal colifonn.
No/100 ml
PH
DO, mg/1
24
71
7.04
0.4
0.96
2.31
7.95
1380
8.2
—
6
12
2.74
0.12
0.16
0.29
2.11
20
8.3
^•^
75
83
61
70
83
87
74
—
—
•^
28.1
38.0
—
5.1
0.02
0.01
3.0
—
7.9
3.0
9.4
17.1
—
2.0
0.11
0.5
2.5
—
8.2
7.4
%
Reduction
67
55
—
60
Negative
Negative
17
—
—
—
*effluent from cell 2
**effluent from cell 4
43
-------
Analysis to determine levels of human pathogenic
microorganisms present in the wastewater and cultured fish were
performed for both systems. Results of a bacteriological study
at Quail Creek showed a reduction of fecal coliform bacteria to
less than detectable levels. No pathogenic bacteria were found
in the wastewater beyond the first two conventional cells, nor
in any of the cells containing fish, or in any of the fish
sampled. Levels of pesticides, heavy metals, and pathogenic
bacteria present in influent wastewater, wastewater from the
fish ponds, and fish flesh were determined in the Arkansas
system. With the exception of the metals copper and mercury,
and staphylococcus bacteria, all samples showed less than the
standard detection limits or were negative.
The same system in Oklahoma was operated the following
year without stocking fish in the final lagoons for a follow-up
comparison study. Coleman noted that a significantly higher
quality effluent resulted with fish present in the system and
that the suspended solids effluent criterion was not met
without the fish. A preliminary study in 1975 at the Benton
site also compared effluent quality from ponds stocked with and
without fish. The flow pattern in the study was arranged so
there were two completely independent,three-pond series, each
receiving half of the total volume. Silver and bighead carp
were stocked in one series. Notable differences in effluent
quality were found in the types of phytoplankton organisms
present and BODc; the effluent without fish was 37.6 percent
higher in BOD5 tnan in the series containing the fish.
On a global basis, fish ponds for sewage purification have
been widespread (References 84 and 92), and a classic example
is the famous sewage fish ponds operated by the Bavarian Power
Company at Munich, Germany, for the production of common carp
to sell for human consumption (References 1 and 93). This
fishery was established in 1929, and for many years provided
final treatment of the pre-settled sewage from the entire city.
The present operation treats only one-third of the city's
sewage. The complex consists of a 7 km (4.35-mile) chain of 30
ponds ranging in size from 4 to 10 ha (11 to 25 acres), and
containing a total area of about 245 ha (600 acres). The ponds
are stocked with common carp of 0.3 kg (0.66 Ib.) initial
weight at a rate of 500 per ha (200/acre), and are operated
over a six-month growing season. Throughout the growing
season, effluent from the settling tank is diluted with river
water at a ratio of 1:3 to 1:6 and fed continuously into the
fish ponds. Retention time in the fish ponds is only about 1.5
days. The BOD5 is reduced from 60 mg/1 in the original pre-
settled wastewater to the range of 2 to 6 mg/1 when it leaves
the fish ponds after dilution. The rate of fish growth is
about 500 kg/ha (450 Ibs/acre) of fish flesh without supple-
mental feeding. The cost of the installation has long been
44
-------
amortized, and the annual net profit from the sale of fish was
estimated at (12,500 in 1970. The entire operation is con-
ducted by only three staff personnel, providing a yield of over
27,210 kg (30 tons) of fish flesh per man year of labor.
Integrated Systems
General Studies—
The perfornence of a five-step biological treatment system
receiving stabilization pond effluent was evaluated by Dinges
to test the feasibility of an integrated system using con-
trolled cultures of higher aquatic plants and animals
(Reference 81). The system consisted of a pH reduction filter
(a novel biological filter intended to reduce the influent pH
to permit zooplankton growth) and a culture unit, 85m (280 ft.)
in length, 90m (30 ft.) in width, and 0.6m (2 ft.) in depth,
divided into four sections by rock barriers. The first pond,
approximately one-half of the culture unit, contained water
hyacinths, snails, and insects. The second pond cultured
zooplankton and was covered with duckweeds to restrict algae
growth. A portion of the second pond was 2.4m (8 ft.) in depth
and aerated by using an airlift pump. Shrimp and fish were
stocked in the third and fourth ponds, .respectively, to feed on
the zooplankton growth and algae regrowth. Theoretical
retention time for the system was 5.3 days. Results for a five-
month period of operation are summarized in Table 13. Loading
rates per unit surface area were calculated by Schwartz
(Reference 15) and based on 118m3/day (31,336 gpd) flow.
TABLE 13. PERFORMANCE OP A FIVE-STEP INTEGRATED TREATMENT SYSTEM FROM JUNE TO
NOVEMBER, 1975 (References 15 and 81)
Hastewater Organic Loading Rate* Influent
Parameter kg/ha/day (Ib/acre/day) mg/1
ECDj 22.7 (20.3)
BODjQ 136.6 (122.0)
OX 106.3 (95.0)
TSS 53.1 (47.4)
Total Organic Kitrogen —
Jdmonia —
Fecal coliform/100 ml —
15
90
70
35
4.8
2.1
1400
Effluent Percent
mg/1 Reductions
3.5
18
40
7
1.2
0.1
10
77
76
43
80
75
95
—
"Calculated based on 118 cu m/day (31,336 gpd) flow.
45
-------
After the initial study period, the system was modified
into a water hyacinth culture basin as the scheme did not
function as anticipated (Reference 65). An inadequate food
supply to support zooplankton production resulted in poor
survival of the stocked animals which feed on the zooplankton.
Extensive research was conducted at the Environmental
Systems Laboratory of the Hoods Hole Oceanographic Institute on
a pilot-scale, integrated tertiary wastewater treatment-marine
aquaculture system (References 94, 95, 96, and 97). Primary
objectives of the research were to develop a process capable of
removing all of the inorganic nitrogen from secondary
wastewater effluent prior to discharge, while culturing
commercially valuable marine organisms. The system was com-
posed of continuous flow-through ponds for the culture of
marine phytoplankton and raceways for the culture of shellfish
and seaweeds. Secondary commercial crops of marine animals,
American lobster, and flounder were stocked in the shellfish
raceways to feed on shellfish wastes and dense populations of
small invertebrates.
Secondary wastewater effluent, mixed with seawater at
various proportions, was used as the. source of nutrients to
culture single-cell marine algae in shallow ponds (132 cu m,
35,000 gallons). The maximum algal production on an ash-free
dry weight basis was estimated at 12 g/sq m/day, with a
nitrogen removal rate of 1.2 g/cu m/day. Based on mean
nitrogen removal rates of 3 kg/ha/day (2.7 Ibs/acre/day) during
the winter and 8 kg/ha/day (7.1 Ibs/acre/day) during the
summer, Ryther projected the area requirement for the algae
pond at 82 sq m/cu m flow/day (77 acres/rogd) in the winter, and
28 sq m/cu m flow/day (26 acres/mgd) in the summer for
secondary effluent with a nitrogen content of 24 mg/1. Algal
production was periodically inhibited by dissolved and parti-
culate organic matter in the secondary effluent, temperature
variations, and protozoan predation.
Harvest from the algal cultures, diluted with 1 to 5 parts
of seawater, was fed into concrete raceways, 12 m by 1.2 IP and
1.5 m in depth (40 x 4 x 5 feet), containing stacked trays of
bivalve mollusks. Initial attempts at. shellfish culture using
American oysters (Crasaostr^a virginica) and hard clams
(Kerccnaria mercenaria) net with little success due to slow
growth rates and high mortalities. The predominate growth of
the algae species of Phaeodactylum trieornutum in the eutrophic
algae cultures was inferior and unsuitable as food for the
shellfish. Inability to control the algal species was overcome
by use of exotic shellfish species capable of utilizing the
kinds of algae that could be mass produced. They included the
Manila clam (Tjmefi japonical. European oysters (Oatrea qdulie)
and Japanese oysters (CraesoBtrea gigus). Related smaller
46
-------
3%p$M*te$&^^ '
scale studies compared the growth of these bivalve mollusks,
along with the mussel
-------
/tj&tWjgi^Jliy^ «-*•
Types of equipment used for hyacinth harvesting include
truck mounted draglines, front-end loaders and backhoes
equipped with clamshell buckets, weed buckets or other
specially designed buckets, single-wide and double-belt
conveyors, self-cleaning bar screens, and solids pumps.
Available equipment can be modified to facilitate harvesting
with the addition of a suitable bucket, chopper or rake.
Boats, over-head reels, and rakes are used to push the plants
toward the harvester. Duckweeds have been harvested by means
of a continuous in-line effluent skimming device followed by
static screening (Reference 102). Equipment selected for har-
vesting should be mobile to allow for the removal of plants
from all portions of the system. Dump trucks, forage wagons,
and small tractors can transfer the harvested biomass to a
reuse area.
Plant material harvested from the system is usually
processed to reduce moisture content. This in turn reduces the
volume of plant biomass and aids in biomass disposal.
Processing is also a necessary percursor to all of the viable
and potential hyacinth produces with the possible exception of
the soil amendment products. Processing may include chopping,
pressing, grinding, or drying. Harvested plants can be chopped
with crimpers, agricultural flail or cylinder shear bar
choppers, or fluid choppers. Incorporating the harvesting and
chopping mechanisms into a single machine has been recommended
(Reference 103). Most of the current research has involved
continuous flow screwpresses, screen presses, and belt filter
presses. Pressed or pre-wilted hyacinths can be dried in
forage, rotary, or solar driers.
Alternative water hyacinth processes and products are
shown in Figure 4. The simplest disposal or reuse method for
hyacinths, and the one presently employed by most of the full-
scale facilities, is use as a soil amendment. Intact or
chopped hyacinths, fresh or composted, have been applied to the
soil as a source of fertilizer and mulch.
Harvesting techniques for animal-based systems are not
well developed and ultimate utilization or disposal of the
harvested biomass has not been given much attention.
Conventional surface and submerged aerators have been
employed in several of the water hyacinth and duckweed systems.
An aeration system consisting of submerged air diffusers was
incorporated into the design of a full-scale aquatic plant
system (Reference 104) and an experimental fish system
(Reference 65).
48
-------
0
8
CO
o
*•
0
g
1
9
0
s
1
o
*
49
-------
The following includes a list of names and addresses of
manufacturers of such equipment. It must be noted that har-
vesting and processing equipment are still being researched and
developed for use in full-scale aquatic plant wastewater treat-
ment systems. Therefore, this list cannot be considered com-
plete. Also, standard harvesting, processing, and wastewater
equipment may be modified to accommodate for the system design.
HARVESTING EQUIPMENT
Aquamarine Corporation
225 North Grand Avenue
P.O. Box 616
Waukesha, HI 53187
414/547-0211
COMPOSTING EQUIPMENT
Resource Conversion Systems, Inc.
9039 Katy Freeway, Suite 300
Houston, TX 77024
713/461-9228
AERATION EQUIPMENT
Hinde Engineering Company
654 Deerfield Road
P.O. Box 188
Highland Park, IL 60035
312/432-6031
Wyss, Inc.
2493 CR 65
Rt. 1
Ada, Ohio 45810
419/634-1971
PROCESSING EQUIPMENT
•
Aeroglide Corporation
7100 Hillsborough Road
Raleigh, NC 27611
919/851-2000
Volusia Tool, Inc.
P.O. Box 904
Lake Helen, PL 32744
904/228-2828
Passavant Corporation
P.O. Box 2503
Birmingham, AL 35201
205/853-6290
Vincent Processors Company
1825 Grant Avenue
Tampa, PL
813/247-6324
R. A. Litkenhaus &
ABSOC., inc.
P.O. Box 16323
Jacksonville, PL 32216
904/737-3536
50
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SECTION 4
TECHNOLOGY EVALUATION
PROCESS CONCEPT
Aquatic Plant Systems
The treatment mechanisms operative in aquatic plant
systems are functions of the existing physical conditions, the
biological habitat resulting from the environment provided by
the plants, and the removal of soluble substances from the
water by plant growth (Reference 65). When aquatic plants,
particularly water hyacinths, assume a primary role in a waste-
water lagoon, the operation of the system is significantly
altered (Reference 68). The algae community is replaced by
rapidly growing macrophytes that convert dissolved organics and
nutrients into a standing biomass which is not rapidly re-
cycled. The hyacinth plant biomass, which remains with the
system, is not present in the effluent.
The culture of aquatic plants in a shallow basin filled
with wastewater results in a unique ecosystem (Reference 65).
The canopy formed by the growth of plant leaves shades the
water surface and minimizes mixing of basin waters by wind
action. The shading also moderates water temperature
fluctuations. The pH level in waters beneath a hyacinth mat
remains neutral. Surface basin waters contain low levels of
dissolved oxygen and bottom waters and sediment are anoxic.
The extensive, fibrous root system of floating macrophytes
extending down into the wastewater provides surface area and a
suitable substrate for a very active mass of organisms which
assist in the treatment. Bacteria, fungi, predators, filter
feeders and detritovores have been reported present in large
numbers living on and among the plant roots. The biological
reduction, oxidation and consumption processes performed by
this complex community in a plant culture basin serve to
stabilize the water by releasing stored potential energy
(Reference 41).
Removal of suspended solids in plant covered lagoons is
accomplished by the natural processes of filtration and
sedimentation which is enhanced in the still waters.
51
-------
Filtration is accomplished by the root systems of the plants,
which physically entrap suspended solids and which are
mechanically removed from the wastewater during harvesting.
Horizontal movement of suspended solids in a basin is inhibited
by the plant roots. This has been illustrated in several water
hyacinth systems in which plant roots growing in the vicinity
of the inlet became covered by an algae slime from incoming
algae cells (Reference 65).
An effective way of reducing suspended solids in lagoon
effluents is by reducing population by allowing almost complete
coverage of the basin with aquatic plants, the plant leaves
shade the water surface and limit algae growth.
The formation of the sludge-like bioroass on plant root
systems also aids in BOD removal. Soluble BOD is removed by
the process of adsorption and incorporation into bacterial cell
mass while nitrogenous BOD is specifically removed by the
plant's utilization of nutrients. The removal rate is
dependent on root absorption and plant metabolic functions in
combination with natural biochemical and physical treatment
mechanisms.
In an aquatic plant system, during the active growth
phase, plants are capable of absorbing soluble organics, heavy
metals, pesticides, and other contaminants. Nitrogen, phos-
phorus, potassium, sulfur, calcium, and other minerals are
incorporated into the plant tissues and can be removed from the
wastewaters to some desirable degree by harvesting the plant
bioroass. Removal of nutrients, such as nitrogen and phos-
phorus, is dependent on plant growth and harvesting rates.
Quantities of these elements essential for plant growth can be
removed in proportion to their composition ratios in the plant
species. Thus the composition of plants, per unit of dry
matter, removed from a wastewater treatment system can provide
an initial estimate of nutrient removal potential.
Nutrient removal in aquatic plant systems, however, is
more complex than uptake by the plant alone. Other responsible
mechanisms include phyBiochemical reactions and uptake by other
organisms growing in the ecosystem. Substrate to support popu-
lations of nitrifying bacteria is provided in the aerobic zone
of a hyacinth basin. Bottom waters and sediment provide a
favorable environment for denitrifying bacteria. Some nitrogen
is also incorporated into the bottom sediment. Phosphorus is
principally removed from wastewater by several chemical ab-
sorption and precipitation reactions occurring primarily at the
sediment layer.
52
-------
Aquatic Animal Systems
The primary treatment mechanism operative in animal-based
aguaculture treatment systems is the control of suspended
solids. By stocking and culturing fish and/or invertebrates in
wastewater treatment ponds, simple organics, algae and sus-
pended particulates are converted into animal flesh. The con-
trol of suspended solids may be accomplished by several
methods. Aquatic animals, such as phytophagous fish or bi-
valves, cultured in wastewaters have the ability to directly
filter phytoplankton out of the water. The addition of zoo-
planktivorous fish to wastewater systems can reduce the zoo-
plankton. The concept of using fishes that feed on different
segments of the plant and animal community in a wastewater pond
is employed in polyculture systems. A controlled ecosystem may
be developed in which organisms are cultured that progressively
feed on higher trophic levels.
The presence of higher aquatic animals in wastewater ponds
produces a system that is more biologically balanced and in
doing so increases the waste treatment capacity of that system
(Reference 92). Both dissolved oxygen and pH are
significantly and consistently higher in wastewater ponds
stocked with fish (Reference 105). The oxygen regime is
improved by fish grazing on plankton which are abundantly
produced in waste-enriched waters. This grazing controls the
phytoplankton blooms and eliminates the typical cycles of
plankton bloom and die-off with the accompanying anaerobic
or low dissolved oxygen conditions in the latter phase.
Raising the dissolved oxygen increases the rate at which the
BOD of the waste is satisfied.
A photosynthesis balance in a wastewater pond also elim-
inates excesses of dissolved carbon dioxide, which depress the
pB. A higher pH is reported to increase the rate of coliforms
reduction in an aquatic system (Reference 106). Increased pH
also improves the effectiveness of the pond as a nutrient trap.
Nitrogen is more readily lost to the atmosphere as NH,, and
phospnates become less soluble and therefore are precipitated
more completely. Thus, both of the changes in dissolved oxygen
and pH within an aquaculture treatment system are improvements
to the operations of a wastewater pond designed to provide an
effluent low in BOD, nutrients and coliform.
The principal wastewater contaminant removal mechanisms in
aquaculture treatment systems are discussed in detail by
Stowell et al., and are summarized in Table 14 (Reference 13).
The effect of each mechanism depends on the design and
management of the aquaculture system, the quality of the
influent wastewater, and climatic and environmental factors.
53
-------
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55
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PROCESS CAPABILITIES AMD LIMITATIONS
Aquatic Plant Systems
Performance—
Water hyacinth systems are capable of removing high levels
.of BOD/ suspended solids, heavy metals/ and nitrogen/ and
significant amounts of trace organics. Hyacinth culture may be
employed as a complete treatment process. Aquatic plant
systems using duckweed show potential in achieving the same
high pollutant removal efficiencies.
The addition of aquatic plants to a wastewater lagoon
system can yield relative stability since the community col-
lectively serves to buffer drastic changes. These systems are
more tolerant of peak organic loadings/ diurnal organic vari-
ations/ and hydraulic fluctuation.
As indicated by the majority of available data/ removal
efficiencies of phosphorus in aquatic plant systems in excess
of 30 to 50 percent cannot be consistently maintained. Phos-
phorus removal will not even approach.that range unless there
are relatively intensive management practices including regular
harvesting of the plants or chemical addition precipitation is
practiced. Removal of phosphorus is limited to the plant
needs. Nutrient ratios in wastewater are not conducive to
complete phosphorus removal/ and nitrogen becomes limiting
before the desired reduction in phosphates is achieved.
Supplemental nitrogen addition to water hyacinth ponds may be a
viable method of correcting this problem (Reference 12, 73).
Temperature and Location Constraints—
As water hyacinths are sensitive to low temperatures/
temperature is the major limitation to the universal use of
this tropical plant for wastewater treatment. Year-round hya-
cinth production in open basins is possible only in the semi-
tropical and warm climates of the United States. Water hya-
cinth systems may be technically feasible in northern climates
if operated in a protected environment/ such as a greenhouse/
or run on a seasonal basis. This has yet to be shown to be
cost-effective for climatic zones where the plant cannot exist
naturally (Reference 14).
Duckweeds are a more cold tolerant plant and offer/ in
theory/ a greater geographical range and longer operational
season than water hyacinths. However/ wastewater treatment
experience with these plants is limited. Many other cold
tolerant aquatic plants exist, but their potential for waste-
water treatment has not yet been evaluated.
56
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By-Product Recovery—
The recovery cf resources from aquatic plant systems
offers a possible means of reducing the cost of wastewater
treatment. Harvested plant biomass can be used in the pro-
duction of fertilizer/soil conditioner, animal feed, or methane
gas. All of these processes are technically feasible/ but, in
most cases, are not sufficiently profitable at this time to
offset the costs of solids disposal (Reference 14).
Reuse Constraints—
The ability of water hyacinths and duckweeds to accumulate
and concentrate toxic materials such as heavy metals and insec-
ticides can limit their suitability as a fertilizer or feed
material. The presence of toxic substances in excessive levels
would make disposal of the solid materials difficult and expen-
sive (Reference 16). There is also a need to determine if
pathogens, particularly viruses, are present in the harvested
and processed plants. Social, political, and economic factors
could also restrict the development of plant residue products.
Evapotranspi ra tion—
Evapotranspiration rates from uncovered hyacinth ponds
have been reported up to six times greater than evaporation
from open water under the same climatological conditions
(References 25, 45, 107). However, these measurements may be
distorted due to the small sizes of the experimental facilities
as claimed by Idso (Reference 108). This controversy needs to
be resolved before uncovered water hyacinth systems are used in
water-short areas.
Odor Problems and Control—
Under conditions of heavy BOD loading, anaerobic con-
ditions may prevail, as the oxygen produced by hyacinths in
photosynthesis is not significant. Although water hyacinths
are not affected by these conditions, odor problems may result.
Mechanical aeration of the basin may be necessary during photo-
synthetically inactive periods to prevent foul odors (Reference
42).
Mosquito Problems and Control-
Mosquito production is encouraged in the quiet waters of
an aquatic plant culture basin. Mosquito control can usually
be effectively handled with Gambusia affinia or other small
surface feeding species of fish stocked in the pond. Dinges
recommended placing small mesh wire enclosures throughout a
basin to provide open areas and enhance fish production
(Reference 41).
The heavy growth of duckweeds may inhibit mosquito
reproduction by preventing mosquito larvae from reaching the
water surface to obtain oxygen (Reference 37).
57
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Hind Problems and Control—
The small size of duckweeds allows the plants to be
readily displaced by wind and wave action thus disrupting
treatment processes. Wind screens and/ or floating barriers
are usually required to maintain a continuous mat of plants on
the surface of a pond (Reference 24). Placement of lagoons in
protected areas or borders of vegetation that alter wind
patterns can moderate such effects (Reference 37).
Land Requirements—
Another restriction on the use of aquatic plants systems
for wastewater treatment would be land area required. As these
systems are land intensive, the size of the community that can
use such a system may be limited.
Legal Constraints—
introduction of water hyacinths or other exotic plants to
areas where it does not currently grow may be influenced by
federal and by state laws in many situations. Public Law 874,
the Grass and Plants Interstate Shipment Act, Amendment to
Chapter 3, Title 18, USC prohibits the interstate transport or
sale of water hyacinths. The inadvertant release of these
plants from a system to local waterways is a potential concern
to a number of different agencies (Reference 14).
Prevention of escape of plants to the open environment by
a fixed barrier in the outfall area of the basin may be one
possible solution (Reference 65).
Aquatic Animal Systems
Performance—
Aquaculture systems consisting of conventional stabili-
zation ponds followed by fish culture ponds have been shown to
be capable of consistently producing secondary or advanced
secondary quality effluent (Reference 15). The major role of
fin fish seems to be suspended solids removal.
Certain fin fish species have demonstrated a potential for
wastewater treatment application and include the carp and
Tilapia species.
Under proper conditions, the treatment efficiency of fin
fish systems should at least be comparable to AWT process
treatments. However, the susceptibility of these systems to
function under a wide number of variables, and their
reliability to handle hydraulic/organic shock loads is unknown
(Reference 109).
58
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Wastewaters nay contain a range of substances that can be
toxic to aquatic animals if present at high enough levels or
remain over a long enough tine to create bioaccunulation
problems. Industrial wastes, detergents, or biocides can
effect the survival and growth of fish in wastewater ponds.
System stability may also be hampered by outbreaks of diseases,
parasites, and unforeseeable climatic conditions. In the event
of a major animal die-off, rate of system recovery may be slow.
Ditsolved Oxygen Constraints—
Dissolved oxygen is one of the most critical environmental
factor which affects the functioning of an animal-based aqua-
culture system (Reference 92, 110). Oxygen levels become
lowest prior to sunrise due to reduced oxygen production at
night from reduced photosynthesis and oxygen uptake by aquatic
plant and animal respiration. When this minimum is below that
required for the cultured species, mortalities occur. Under
minimal dissolved oxygen, fish species are also susceptible to
stress from substances which they can otherwise tolerate under
higher oxygen levels. Increased BOD and temperatures can also
reduce the dissolved oxygen levels in wastewater ponds.
Mechanical aeration systems can be used routinely or on a
standby basis in wastewater aquaculture systems to eliminate
fish stress or losses during expected periods of low oxygen.
Temperature Constraints—
The use of Tilapia spp. may be restricted in cold climatic
areas due to their limited tolerance to low temperatures. The
lower lethal temperature for these tropical fish species ranges
from 10 to 13°C. The use of cold-adapted species which show
potential for wastewater treatment needs to be evaluated.
In addition, only a few species of filter-feeding
shellfish remain active at temperatures below 15°C, and even
those become dormant at temperatures below 5°C.
By-Product Recovery--
Wide variations of fish production in wastewater ponds are
indicated and are related to differences in the amount of fish
initially stocked and prevailing environmental conditions in
the culture unit (Reference 15). However, the benefits to fish
culture, especially increases in fish yield, by using waste-
waters ere well documented (Reference 110). Thus, potential
exists for generating large quantities of by-products from
these systems.
Suggested utilization of fish products from wastewater
aquaculture systems include direct human consumption, animal
feed, and extraction of protein. These products have not been
certified (or uncertified) by the USDA for use as yet, and the
59
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technical and economic feasibility of protein extraction has
not been adequately demonstrated (Reference 15). Schemes in
which direct use by human beings is avoided include fingerling
fish for commercial growers, and bait fish for sportsmen
(Reference 110).
Reuse Constraints--
Potential public health problems in the areas of disease
transmission and contamination pose a significant barrier to
the utilization of wastewater products as food stuffs in this
country (Reference 10). Research on fish as a possible vector
of human pathogenic bacteria, viruses, protozoans and helminths
associated with enteric diseases will be required before D.S.
FDA will permit these fish for human consumption (Reference
111, 112). Filter-feeding species are known for their ability
to concentrate pathogenic organisms; however, these pathogens
are found only in the mantle cavity and gut. Also, fish cannot
act as intermediate hosts to the vast majority of human
parasitic agents and the only way transmission may be effected
is by direct transfer from the pond onto the fish scales or
into its gut (Reference 113). Fish or.animal species carrying
pathogens may be depurated by keeping them in clean water for a
period of time prior to marketing. Raising fish in diluted
wastewater for human consumption has been the practice in
Munich and other places.
While potential exists for preventing transmission of
pathogens, wastewater products are also in danger of
contamination by heavy metals, organic compounds, and other
industrial wastes which may have carcinogenic, mutagenic, as
well as teratogenic effects (Reference 111). Trace
contaminants may also reach toxic concentrations when accumu-
lated in the food chain. Permissible levels of heavy metals in
treated effluent used for aquaculture have been recommended by
Kerfoot and Jacobs (Reference 114) and Kerfoot and Refmann
(Reference 115).
Probably the most critical drawback to products grown in a
wastewater medium is that of public acceptance. Many of the
social, economic, health, and political factors which influence
consumer behavior in this regard have been identified
(References 116 and 117), and specific marketing strategies are
discussed by Buguenin and Little (Reference 118).
Land Requirements—
Another major constraint in the utilization of wastewater
aquaculture treatment systems is their large land requirement.
Systems involving higher forms of aquatic animals may be even
more land intensive than their aquatic plant counterparts.
60
'?**
»
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Legal Constraints—
Introduction of exotic fin fish species, such as the
members of the carp group and Tilapia spp., to waters where
they do not naturally occur may be influenced by federal and
state laws in many situations.
The inadvertant release of these fish from a system to
local waterways and their possible adverse effect on local
species and environments are potential concerns to a number of
different agencies. This limitation could be eased if research
emphasis would be placed on native species of fish which also
show potential in wastewater treatment. The Sacramento
blackfish (Orthedon microlcd ipotus). buffalo fish (Ictiobus
spp.) and members of the Cyprinidae family are some of the
North American fishes that seem to be largely herbivorous and
are also hardy.
The Food and Drug Administration, particularly through the
Delaney Amendment banning any additive found to induce cancer
in humans, could play a major role in determining the
feasibility of by-product recovery in wastewater aguaculture.
Additional health-related standards will have to be satisifed
if by-products become part of the food chain (Reference 119).
Marine vs. Freshwater Systems--
Freshwater systems have a distinct advantage over marine
systems for wastewater treatment application (Reference 10).
Since wastewater effluents are more similar in salinity to
freshwater than seawater, freshwater organisms may be cultured
using undiluted effluents, whereas marine systems require
extensive seawater dilutions in order to maintain a favorable
salinity range for the culture organisms.
Culture Constraints—
Establishing reliable culture techniques for integrated
wastewater treatment processes have been particulary difficult
this far. System instability due to predation of low level
organisms and lack of species control will have to be overcome
before the system's treatment effectiveness can be evaluated.
Ryther et al. provided an excellent discussion concerning
the factors which influence the development of aquatic
populations in highly enriched marine environments (Reference
120). In general, the authors concluded that enriched marine
systems are relatively unstable, failing to develop a fully
diversified community and that a high degree of control and
management is required to avoid inefficiencies and detrimental
effects.
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DESIGN CONSIDERATIONS
Design considerations for aquaculture treatment systems
may be more complex than those for conventional systems as more
variables are involved and many are beyond the direct control
of man. In order to design an aguaculture syste», an under-
standing of its physical characteristics, engineering criteria,
: and treatment capabilities as a function of system constraints,
; and by-product disposal/utilization are necessary (Reference
121). Aquatic organisms selected for culturing in the treat-
ment systems must be capable of removing contaminants while
surviving variable climatic and wastewater conditions. The
design of the aquaculturei treatment system should be formu-
lated to provide the environment necessary for the selected
I aquatic species to function as intended. The recovery of
resources will also effect the design of these systems.
j
i The selection of aquatic plants and animals to be used for
i wastewater treatment is based, to a large extent, on their
'"ability to provide and maintain an environment in which waste-'
i water treatment will occur. Because the functional performance
! of whatever aquatic species are used will depend on their
j growth and behavior, the impact of factors affecting growth and
! behavior, 'such as wastewater characteristics, local
'. environmental conditions, and operational and managerial
j practices must be known. Other site-specific factors in
j addition to wastewater treatment potential, environmental
suitability, and species manageability may need to be
considered when selecting organisms for use in wastewater aqua-
culture treatment systems.
Adequate data exist to assist in the design of water
hyacinth wastewater treatment systems, especially for small
capacity systems where the climate is moderate (Reference 16).
Reliable engineering criteria appear to be available to
justify the design of such systems for treating primary ef-
, fluent, for upgrading existing systems, for advanced secondary
: treatment, and for full advanced wastewater treatment
(Reference 14). Full-scale systems that are currently in
operation and new systems being constructed should generate
additional data to refine the criteria that will be presented
in this section. :
| There is sufficient information available to install fish
culture units in the final cells of stabilization ponds.
However, there are not enough data available at this time to
permit routine design of such units for wastewater treatment
(Reference 14). Species-specific removal rates and growth j
rates under different environmental and wastewater conditions j
need further definition (Reference 15). Most of the other i
aquaculture systems reviewed in Section 2 have not been
I
62 !
i
i
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developed or studied sufficiently and should be considered to
be in the exploratory or developmental stage. Thus, it is too
early at this time to formulate even general applicable
criteria for designing a reliable system. Persche, in his
assessment of combined aquaculture systems/ stated that firm
design criteria may not be attainable practically, since some
of the variables that affect system design are greatly
influenced by site-specific conditions (Reference 109). The
author concluded that the use of general guidelines coupled
with long-term pilot studies at the proposed site may be the
best approach to attaining optimum system design.
The criteria generally considered in the design of
wastewater stabilization ponds, particularly physical factors,
can be applied to the design of aguaculture treatment systems.
These criteria are discussed in several commonly used design
manuals (Reference 122). Most conventional lagoon systems can
be converted with little or no modification to aquaculture
systems, to upgrade effluent quality to the level of secondary
or advanced secondary treatment (Reference 15). Water hyacinth
wastewater treatment technology is based upon essentially the
same design procedures as those for stabilization ponds.
The following design parameters should be considered and
evaluated in the development of an aquaculture wastewater
treatment system:
o Location, climate, temperature
o Site requirements
o Land requirements
o Wastewater characteristics
o Pretreatment
o Post-treatment
o Pond or raceway: basin size, number, and configu-
ration
o Organic and surface loading rates
o Hydraulic residence time (detention time)
o Hydraulic loading rates
o Recovery, use or disposal of harvested biomass
o Others
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These parameters are further defined for application in
water hyacinth treatment systems. Procedures presented in a
design manual for water hyacinth wastewater treatment by Gee
and Jenson Engineers are also summarized for each of these
parameters (Reference 43).
Location. Climate. Temperature
Water hyacinths should not be considered for areas where
freezing conditions prevail during the winter, unless provi-
sions are made to protect the plants from freezing or alter-
native treatment methods are available during the winter.
Without such provisions, hyacinths should only be considered
for year-round use in southern and coastal areas where temper-
atures are adequate for growth.
All of the water hyacinth systems in the United States
that are currently treating wastewater are located in semi-
tropical or warm temperature climates. The benefits of a
system in a colder climate need to be investigated on a large
scale to establish the economics as well as the operational
problems, as recommended by Middlebrooks (Reference 16).
System enclosures should allow for harvesting and
cleaning. The option of removal during warmer months should be
evaluated. Covers should be sturdy and durable, preferably
constructed of rigid plastics or frame mounted plastic sheets.
Site Requirements
The selection of a location for culture basin construction
should be based on an evaluation of several site specific
variables. The availability of sufficient land area for the
.hyacinth basins and any related treatment and disposal systems
is the prime consideration. Other factors to be considered are
the accessibility of the site, hydrogeologicel characteristics,
and the method and location of final effluent disposal.
Land Requirements
All of the water hyacinth wastewater treatment systems
presently operating are less than 4 hectares (10 acres) in
surface area and the majority of the systems are less than 1 ha
(2.5 acres) in surface area (Reference 16).
Hany researchers have suggested that ponds ranging from 1
to 2 ha per 1000 cu m/day (10 to 20 acres per mgd) will provide
sufficient area for secondary treatment of primary effluent and
advanced treatment of secondary effluents. Reed et al.
reported that based on current experience, a pond surface area
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of approximately 1.6 ha per 1000 cu in/day (15 acre per mgd)
seemed to be reasonable for treating primary effluent to
secondary or better quality (Reference 14). For systems
designed to polish secondary effluent to achieve higher levels
of BCD and suspended solids removal, an area of about 0.5 ha
per 1000 cu in/day (5 acres per mdg) should be suitable. For
enhanced nutrient removal from secondary effluent an area of
approximately 1.3 ha per 1000 cu m/day (12 acres per mgd)
seemed to be reasonable. A summary of these land requirements
is found on Table 15.
TABLE 15. LAND REQUIREMENTS FOR WATER HYACINTH WASTEWATER
TREATMENT SYSTEMS.
Treatment
Land Requirements
ha per
1000 cu m/day acres/mgd
Secondary treatment and advanced
treatment of secondary effluents
Primary effluent to secondary or
better quality
Polish secondary effluent
Nutrient removal from secondary
effluent
1 to 2
1.6
0.5
1.3
10 to 20
15
5
12
Wastewater Characteristics
The characteristics of the influent wastewater and re-
quired effluent quality must be established to properly size
the hyacinth pond system. Influent water quality parameters of
concern include BOD5, total suspended solids, nitrogen and
phosphorus, temperature, pH, dissolved oxygen, chlorides, and
toxic compounds, particularly if a portion of the influent
wastewater is from industrial sources. The values obtained for
these parameters should be compared against the range of
tolerances for water hyacinths or other potenial aquatic plant
species. The required effluent water quality will vary
depending on the local conditions and applicable discharge
regulations.
65
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Pretreatment
Pretreatment of the influent wastewater prior to treatment
by hyacinths or other aquatic plants may be desirable or
necessary. Pretreatment may consist of one or more processes,
including aeration, screening, grinding, primary settling, and
chemical treatment. However, it is not always necessary to
provide pretreatment in an aquatic plant system.
Post-Treatment
Post-treatment of the effluent from an aquatic plant
culture basin may be necessary to meet the final effluent
requirements prior to discharge. Post-treatment may include
disinfection, filtration, sedimentation or other processes.
Aeration may be necessary to prevent odor problems resulting
from anaerobic conditions in hyacinth ponds. The addition of
chemicals may be required to remove phosphorus remaining in the
effluent.
Pond Size. Number, and Configuration
The considerations for pond size, number, and config-
uration are based on selected harvesting practices and routine
maintenance. Optimal design of culture basins is necessary to
minimize area requirements, and in temperate climates, green-
house costs. The physical characteristics of optimal hyacinth
culture basins were previously described in Section 1.
Organic and Surface Loading Rates
The organic loading rates used for water hyacinth treat-
ment systems are similar to those used for conventional
stabilization ponds. However, the effluent from the plant
system may be better in quality than from a stabilization pond.
The basic criteria used to design water hyacinth ponds for
secondary treatment of primary effluent, based on Wolverton's
research, are the organic uptake tate and the pond surface
loading. A design value of 5.0xlO~4 Kg BOD5 per Kg wet plant
mass per day (5.0xlO~* Ibs BOD5 per po.und wet plant mass per
day) was recommended (Reference 42).
Kith water hyacinths, BODc loadings up to 150 Kg per ha
per day (134 Ibs per acre per Say) can be used, assuming an
average standing crop of 225 metric tons per ha (111 tons per
acre). With densely packed hyacinths and 100 percent coverage,
surface loading rates of up to 225 Kg BODc per ha per day (200
Ibs BOD5 per acre per day) may be used (Reference 43). The
recommended surface loading rate for ponds where at least 80
percent plant coverage can be maintained ranges from 56 to 225
Kg BOD5 per ha per day (50 to 200 Ib BOD5 per acre per day),
66
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with a recommended design value of 140 Kg BOD5 per ha per day
(125 Ibs BOD 5 per acre per day) (Reference 43).
In reviewing the current full-scale water hyacinth
treatment facilities, Middlebrooks reported that organic
loading rates of less than 30 Kg/ha/day would provide
satisfactory results when processing raw wastewater (Reference
16). Water hyacinth systems receiving secondary effluents or
stabilization pond effluents are more numerous, and a much
wider range of organic loading rates have been employed with
these systems. Organic loading rates applied to the first
basin in hyacinth systems have ranged from 31 Kg/ha/day to 197
Kg/ha/day. All of these systems produced an effluent which
would satisfy the secondary standards of 30 mg/1 for BOD5 and
suspended solids (Reference 42). Table 16 summarizes the
various organic loading rates.
TABLE 16. ORGANIC LOADING RATES FOR WATER HYACINTH TREATMENT
SYSTEMS. (Reference 42, 16, 43)
Condition
Rate
Average standing crop of 225
metric tons per ha
100% coverage
80% coverage
Processing raw wastewater
First basin in hyacinth system
150 Kg BOD5/ha/day
225 Kg BOD5/ha/day
56 to 225 Kg BOD5/ha/dayj
design value:
140 Kg BOD5/ha/day
Less than 30 Kg BOD5/ha/
day
31 to 197 Kg BOD5/ha/day
Comparison of several water hyacinth systems indicated
that there is a direct correlation between surface loading
rates and nutrient removal efficiencies. Design curves based
upon these data have been drawn up by Gee and Jenson Engineers
to address nutrient removals in hyacinth tertiary treatment
systems (Reference 43). Effluent requirements for nitrogen and
phosphorus concentrations are used to determine the required
removal efficiencies for these nutrients and thus the
corresponding surface loading rates.
67
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5_Residence Time (Detention Time)
rA critical factor in aquatic plant pond design, with
regard to treatment efficiencies for either secondary or ter-
tiary systems is the contact time with the root zone of the
hyacinth. It is important to allow enough time for adequate
sorption, filtration, and nutrient utilization. Typical
detention times for a secondary hyacinth treatment system
treating primary effluent range from six to seven days, plus an
allowance for sludge storage and peak flows. In a tertiary
system, minimum detention times range from one day for a sur-
face loading of 0.2 ha per 1000 cu m/day (two acres per mgd) to
5.5 days for a surface loading of 1.2 ha per 1000 cu m/day (11
acres per mgd).
Most of the studies which reported detention time for
water hyacinth systems are based upon theoretical calculations
(Reference 16). The degree to which the actual hydraulic
residence time approaches the theoretical depends upon the care
with which the original design was carried out. Tracer studies
of the existing systems to determine actual detention times
have been recommended.
Hydraulic Loading Rates
Based upon the results currently available, it appears
that a hydraulic loading rate of 2000 cu m/ha/day when treating
effluent will produce an effluent quality that would
advanced secondary standards (BODc110 mg/1, TSSilO
TKN15 mg/1, and TPi5mg/l) (Reference 16). With nutrient
removal as the principal objective, a shallow pond (£0.4m) and
a hydraulic loading rate of approximately 500 cu m/ha/day
should produce good nitrogen removals (
-------
a<
•
nterfere with the performance or reliability of the aquatic
"ant system.
Methods of harvesting hyacinths were described in Section
2; additional information on the harvesting program will be
presented in the following section under system operation and
maintenance.
Other Parameters
Additional factors may need to be addressed when designing
an aquatic plant system. These include sludge accumulation and
storage, evapotranspiration, odor production and control,
vector insect control, and other site-specific factors.
Kiddlebrooks in 1980 summarized design characteristics of
the known aquatic plant systems that were constructed or modi-
fied to treat wastewater (Reference 16). Values were recom-
mended to assist in the design of a system capable of producing
an advanced secondary effluent. Table 17 presents the recom-
mended design criteria.
Similar design criteria were recommended by Dinges for the
construction of hyacinth basins for upgrading stabilization
pond effluent in the State of Texas (Reference 41). Wolverton
proposed two designs for sewage lagoons using water hyacinths
and duckweeds to treat domestic wastewater. One was for small
ommunities of 500 people or less and the other for communities
,f 1000 to 3000 people (Reference 42). The proposed desicn
Characteristics addressed four problems: sludge accumulation,
odor control, BOD reduction, and total suspended solids
removal.
Few mathematical models have been produced by the research
on wastewater treatment with water hyacinths. Cornwell et al.
proposed two design equations for nutrient removal by corre-
lating nitrogen and phosphorus removal to pond surface area and
flow (Reference 34). Stewart found that water hyacinths grow
exponentially with time and he used the Michaelis-Kenten
kinetic equation to correlate the growth rate with limiting
nutrient concentration (Reference 73). However/ the attempts
to correlate hyacinth growth rate kinetics with nutrient uptake
rate as a basis for design have failed to produce a practical
general design equation due to the many environmental variables
that must be considered for each site (Reference 43).
ENERGY ANALYSIS
An aquaculture treatment system employs a minimal amount
of equipment, and therefore, has relatively low operational
69
I
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TABLE 17. DESIGN CRITERIA FOR WATER HYACINTH WASTEWATER TREATMENT SYSTEMS
OPERATED IN WARM CLIMATES BASED UPON BEST AVAILABLE DATA
(Reference 16)
Parameter
Design Value
Metric English
Expected
Effluent
Quality
A. Treating Raw Wastewater To Meet Secondary Requirements
Hydraulic Residence Time
Hydraulic Loading Rate
Depth/ Maximum
Area of Individual Basins
Organic Loading Rate
Length to Width Ratio of
Hyacinth Basin
Water Temperature
Mosquito Control
Diffuser at Inlet
Dual Systems/ Each Designed
to Treat Total Flow
> 50 days > 50 days
200 cu m/ha/day 0.0215 mgd/acre
£ 1.5 meters £ 5 feet
0.4 hectare 1 acre
1 30 kg BOD5/ i 26.7 Ibs
ha/day BOD5/ac/day
SS £30 mg/1
> 3:1
> 10°C
Essential
Essential
Essential
> 3:1
> 50°F
Essential
Essential
Essential
B. Treating Secondary Effluent to Advanced Secondary
Hydraulic Residence Time
Hydraulic Loading Rate
Depth/ Maximum
Area of Individual Basins
Organic Loading Rate
Length to Width Ratio of
Hyacinth Basin
Water Temperature
Mosquito Control
Diffuser at Inlet
Dual Systems, Each Designed
to Treat Total flow
Nitrogen Loading Rate
> 6 days > 6 days
800 cu m/ha/day 0.0855 mgd/acre
0.91 meter 3 feet
0.4 hectare 1 acre
1 50 kg BOD5/ £ 44.5 Ibs
hi/day BODc/ac/day
SS
TP
TO
mg/1
mg/1
> 3:1
> 20°C
Essential
Essential
Essential
i 15 kg TKN/
ha/day
> 3:1
> 68°F
Essential
Essential
Essential
i 13.4 Ibs
TKN/ac/day
70
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requirements as compared to a conventional treatment plant.
Energy ie required for pumping (in some cases)/ harvesting
equipment and trucks for hauling harvested solids.
Pumping may be required for static lift between the pre-
treatment effluent discharge and the aquaculture system inlet,
and/or to provide gravity flow through the aquaculture basin.
A reasonable range would be between 0 and 3 meters (C to 10
feet) of head. The energy required will be a function of the
amount of hours the pumps will be in operation.
Table 18 summarizes the power and energy demands at
various flows and for the conservative conditions of a 3 meter
static lift and continual operation (24 hours a day/ 365 days a
year). The table shows that the annual pumping energy demands
are quite small.
TABLE 16. PUMPING ENERGY DEMANDS FOR AN AQUACULTURE SYSTEM/
ASSUMING A 3 METER STATIC LIFT
Flow cu m/day
kwc
MJ/yearb
kwh/yearb
400
800
2000
4000
8000
0.170
0.34
0.85
1.7
3.43
5,364
10/728
26/820
53/640
107/280
1/490
2/980
7/450
14/900
29/800
^Assuming a wire to water pumping efficiency of 80 percent
DFor continuous use; 365 days a year and 24 hours a day
There are many potential methods of harvesting the water
hyacinths. The estimate herein is based on a conventional
aquatic weed harvesting system. This may not be a reasonable
assumption for the smaller systems where ftirly simple har-
vesting techniques may be used/ but for this cost and energy
analysis some assumptions and simplifications must be made.
This system includes a harvester and a shore conveyor which is
fully automatic and requires only one operator to drive the
harvester. The shore conveyor conveys the harvest back up onto
the land where it is dropped into a dump truck. The following
assumptions were used in the estimate:
o Earvesting volume * 440 wet metric tons/ha/year
o Harvesting capacity » 2.27 metric tons/load
o Total operating time/ including harvesting/ unloading
and transport » 0.66 hours/wet metric ton or 290
hour/ha/year
71
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o The harvester and conveyor are driven by small
gasoline engines.
o Energy requires 1.58xl05 kJ/hour (44.0 kwh/hour)
Therefore, the energy required is 9.18xl07 kj/ha/year
(1.03xl04 kwh/acre/year).
The harvested solids are assumed to be disposed of on-
site, either by land application or in a landfill. The
estimates for energy consumed in solids disposal are based on
the following:
o A 1.6 kilometer (1 mile) round trip between hyacinth
pond and disposal area.
o Dump truck fuel efficiency of 2.13 kilometers/liter
gasoline (5 miles/gal).
o Each load is 2.7 m.t. (3 tons).
Therefore/ the energy for solids disposal is 3.44xl06
kj/ha/year (386 kWh/acre/yr). The. total energy required for
harvesting and disposal is 9.52x10' kJ/ha/year (1.07x10* kWh/
acre/year, 364 gal/acre/year).
For this energy analysis it is assumed that the harvested
solids have no potential value. This is based on the fact that
none of the full scale facilities are deriving any financial or
energy value from the harvested solids. The Reedy Creek
Facility is studying the anaerobic digestion of water hyacinth
at a bench scale level.
OPERATION AND MAINTENANCE REQUIREMENTS
Aquaculture treatment systems function under a number of
variables, many of which are beyond the control of the
operator. Therefore/ operation and maintenance requirements
are minimal for these systems/ with only a few control
variables required for the adjustment of treatment efficiency.
The process variables that can be controlled allow the system/
if properly designed, to be operated at a constant design
efficiency.
O&M practices for aquaculture treatment systems will vary
depending on the species selected. The match between the
environment, as determined by wastewater characteristics and |
climate/ and the environmental requirements of the selected
species needed to optimize their function in the treatment
process will rarely be perfect. Tchobanoglous et al. reported
72
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that managerial practices are an additional aspect of the
aquaculture concept that, if applied, can create an environment
closer to the optimum for the selected species. These may
include pretreatment of the wastewater, aeration, controlled
recirculation, control of residence times, and biomass har-
vesting (Reference 121).
Control of water hyacinth treatment systems is accom-
plished by pl;.\n<: harvesting, basin cleaning, and, to a lesser
extent, control of environmental conditions and influent
characteristics (Reference 43). Eyacinth and sludge processing
sri<3 disposal should also be considered during design as an
important O&K factor. Odor, insect, and other nuisance
conditions may develop and have to be controlled.
The frequency of plant harvesting is dependent upon the
required effluent quality, plant condition and climatic
factors. Generally, more frequent harvests will be required
during the hotter months of the year. In colder regions where
only seasonal operation will be permitted (unless adequately
protected), all hyacinths should be removed from the culture
basins during the freezing period to prevent the hyacinths from
dying and settling to the pond bottom. During periods of
accelerated plant growth, it has been recommended that har-
vesting be performed at least once every two weeks. Hyacinths
that exhibit a slower growth rate, leaf yellowing, or other
unhealthy characteristics should be removed from the culture
basins- during harvest. Systems designed for secondary treat-
ment can be harvested less frequently. However, they may need
to be harvested at least once per month during hotter, rapid
growth periods of the summer season.
The optimum harvesting program should be predicated on a
hyacinth removal rate that maintains a constant coverage in the
ponds. Where constant coverage is not practical, the
harvesting program should be based upon observations and
measurements of the system effluent quality and plant
condition, in order to prevent algae blooms and to maintain an
adequate treatment efficiency at all tiroes, it has been
recommended that no more than 20 percent of the pond surface
area be harvested at any one time.
A wastewater management system is complete only with pro-
per disposal or utilization of residual by-products. Harvested
water hyacinths may need to be processed following harvesting
to reduce the moisture content and bulk of the plants to
simplify disposal/reuse. There are several alternative
disposal methods suitable for properly processed hyacinths.
Processing methods and disposal/reuse alternatives have been
previously discussed in Section 2.
73
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Basin cleaning may be necessary to prevent excessive
build-up of solids and plant debris on the basin bottom.
Sludge accumulation in hyacinth ponds does not appear to be a
significant problem since the solids undergo decomposition.
However, ponds that may accumulate excessive solids need to be
taken out of service, emptied and cleaned as necessary to
prevent reductions in removal efficiency. Tertiary treatment
ponds should be cleaned as required to maintain adequate treat-
ment efficiency. Secondary treatment systems should be cleaned
at least once every five to ten years, or as required by the
accumulation of sludge and solids deposits' on the basin bottom.
COST ANALYSIS
Cost estimating procedures used in this report follow the
U.S. EPA1 s cost-effectiveness guidelines (Reference 123). Cost
effectiveness is defined to include monetary cost and environ-
mental and social impact assessment. Capital cost estimates
are based on the Engineering News Record Construction Cost
Index (EKR CCI) 20 cities average, March 1981. Capital costs
are based on an operable system with a 20-year life. If a
system has an expected service life of less than 20 years, the
O&N cost includes the annual present worth of subsequent
replacement required to obtain a 20-year service life. Salvage
value for estimated service life beyond 20 years is considered
for land as allowed by the EPA guidelines.
Capital costs include construction, engineering, legal,
administration and contingencies for all building, equipment
and appurtenances. Annual operation and maintenance costs
include labor, energy, chemicals and routine replacement of
parts and equipment. Equipment cost estimates were based on
preliminary layouts and sizing, appropriate redundance,
quotations from equipment manufacturers and recent contract
bids as available. Operating cost escalations are projected to
be approximately 10 percent per year. The assumptions made for
the energy estimates in the previous energy section apply.
Basic cost assumptions include:
Service life « 20 years
Life cycle cost
interest rate (EPA required) « 7 percent
74
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Non-component costs
Non-construction costs
Capital cost
Capital recovery factor
Present worth factor
ENR CCI (20 cities average
March, 1981)
Labor cost, rural community
(March, 1981)
Energy cost (March, 1981)
Electricity (industrial
rate)
Gasoline
Energy cost escalation factor
Electricity
1980-1990
1990-2000
Gasoline
1980-1990
1990-2000
Piping £ 10%
Electrical i 8%
Instrumentation @ 5%
Site preparation @ 5%
Total«28%of
construction costs
Engineering and con-
struction supervision
@ 15%
Contingencies @ 15%
Total-30%of
construction and non-
component costs
Construction cost
plus non-component
and non-construction
costs
20 years, 0.09439, 7%
10.594 times
annual operating cost
3384
$ll/hour
$.011/MJ
($0.04/kilowatt hour)
$0.396/liter
($1.50/gallon)
28%
6%
34%
21%
In order to estimate the costs which are associated with
an aquaculture system, assumptions were made to narrow the wide
range of possibilities. The capital and O&M costs of an aqua-
culture system are based primarily on the type of system
(aquatic macrophytes, invertebrates, integrated, etc.) and the
necessary surface area. Of the four categories of aquaculture,
75
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aquatic plants are the most developed, and specific design
criteria have been published for these systems. Within the
aquatic plants category, the most work has been done on water
hyacinths. Since the most reliable data have been developed
for water hyacinth systems, they will be used for the cost
evaluation.
Hyacinth systems are sized on surface and organic loading
rates. These rates vary for different influent and effluent
quality. Three probable applications have been developed for
the cost evaluation to illustrate how costs relate to the
varing degrees of treatment.
Case li
Treatment Quality
Concentrations (mg/1)
BOD5 TSS N P
Influent - Primary effluent 150
Effluent - Secondary 30
100
30
40
40
8
8
Design Criteria from Table 17:
Organic loading « 100 kg BODc/ha/day, 89 Ib BODr/acre/day
Depth « 1.5m, 5 ft
Therefore:
Surface loading = 1.5 ha/1,000 cu m/day, 14 acre/mgd
Volume » 2.25xl04 cu m/1,000 cu m/day
Case 2t
Treatment Quality
Concentrations (mg/1)
BOD5 TSS N P
Influent - Secondary effluent 30
Effluent - Advanced secondary 10
30
10
40
10
8
5
Design Criteria from Table 17:
Organic loading « 50 kg BOD5/ha/day, 47 Ib BODc/acre/day
Depth - 0.91 m, 3 ft
Therefore:
Surface loading « 0.6 ha/1,000 cu m/day, 5.6 acres/mgd
Volume - 5460 cu m/1,000 cu m/day
76
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Case 3 t
Treatment Quality
Concentrations (ntg/1)
BOD5 TSS N P
Influent - Advanced Secondary 10 10 10 5
Effluent - AWT 5 5 3.5 3.5
Design criteria based on the results frcm full scale
application at Lakeland, PL and Coral Spring, PL.
Surface loading « 2.64 ha/1,000 cu m/day, 24.6 acre/mgd
Depth • 0.5m, 1.6 ft
Therefore:
Organic loading « 3.78 kg BOD5/ha/day, 3.37 Ib BOD5/acre/day
Volume « 1.32xl04 cu m/1,000 cu m/day
Based on the above values the total surface area was
computed and is tabulated in Table 19.
TABLE 19. SURFACE AREA REQUIRED FOR WATER HYACINTH AQUACULTURE
SYSTEMS, HECTARES
Flow (cu m/day) Case 1 Case 2 Case 3
(Secondary) (Advanced Secondary) (AWT)
400
800
2000
4000 .
8000
0.6
1.2
3
6
12
0.24
0.48
1.2
2.4
4.8
1.1
2.1
5.0
11.
21.
Capital costs include earthwork, land acquisition, pumps,
harvesting equipment, greenhouse structure, and artificial
liners.
To obtain advanced waste treatment (AWT) from an influent
of primary effluent the three cases can be added in series.
Other combinations are also possible.
The major construction cost is for earthwork which in-
cludes excavation, grading, berm construction, and compaction.
The current cost is approximately $6.50/cu m ($5/cu yd). Table
20 lists the approximate cost of earthwork, for various flows,
for all three cases. The total present worth cost of a new
aquaculture system is roost sensitive to the earthwork cost. If
77
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existing basins or ponds are used, earthwork cost becomes less
significant.
TABLE 20. COST ESTIMATES OF EARTHWORK FOR WATER HYACINTH
AQUACULTURE SYSTEMS, $ THOUSAND, ENR CCI 3384*
Flow (cu m/day)
400
800
2000
4000
8000
Case 1
$ 58.5
117
293
585
1,170
Case 2
$ 14.3
28.3
73.3
142.7
285
Case 3
$ 34
69
172
343
690
* Based on 56.50/m3 of excavation
The cost of land acquisition varies across the country.
While some agencies already own available land, others must
purchase a suitable site. In addition, many aquaculture
systems involve conversion of existing pond systems. The esti-
mated range for land purchase used in this analysis is $2,470-
4,942 per hectare ($1,000-2,000 per acre). Since aquaculture
systems are land intensive it is important to consider the cost
of land where applicable for a specific system cost analysis.
Table 21 summarizes the range in land acquisition costs for the
three cases at various flows. The salvage value of the land is
considered in the present worth cost analysis.
The sensitivity of the total present worth cost of an
aquaculture system to land acquisistion cost was evaluated
using the design examples presented in Tables 27, 28, and 29.
The land acquisition cost of $3,000/ha ($l,335/acre) was used
for these tables resulting in about 1 to 2 percent of the total
present worth cost. If land acquisition cost were increased
ten-fold to $30,000/ha ($13,350/acre), the percent of total
present worth cost would be 9 to 10 percent.
A portion of the land acquisition cost (about 50 percent)
is recovered in the analysis as a salvage cost. As allowed by
grant regulations, land values can be appreciated at a compound
interest rate of 3 percent/year over the planning period (20
years in this case) or a factor of 1.806. The present worth of
the salvage value at the end of 20 years is calculated by
multiplying that value by the single payment present worth
factor at 7 percent for 20 years or 0.2584. The salvage value
(land value at the end of 20 years) therefore reduces the
impact of land acquisition cost or the total present worth cost
of the aquaculture system. If existing facilities are used
78
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(e.g. oxidation ponds), then land acquisition costs are not
significant.
TABLE 21. COST OF LAND ACQUISITION FOR WATER HYACINTH
AQUACULTURE SYSTEM, $ THOUSAND, ENR CCI 3384*
Flow (cu m/day) Case 1 Case 2 Case 3
400
800
2000
4000
8000
$ 1.5-3.0
3.0-6.0
7.4-14.8
15-30
30-60
$ 0.5-1.2
1.3-2.4
3-6
6-12
12-24
$2.5-6.0
5-10
12.6-24
27-64.3
54-98.8
* Based on $2,500 to $5,000 hectare
If pumping is required, capital expenses will be encoun-
tered for pumps, a pump station and piping. Approximate
capital costs associated with pumping are shown on Table 22.
The cost of the harvesting equipment is based on the
system described in the preceding section. The total capital
cost is about $91,000, which can be broken down to $69,500 for
the harvester, $16,000 for the shore conveyor and $5,500 for
the trailer.
TABLE 22. CAPITAL COST OF PUMPS, PUMP STATION AND PIPING, ENR
CCI 3384 (Reference 125)
Flow Cost
cu m/day $1000
400 21.5
800 33
2000 44
4000 82
8000 123
A dump truck will be used for hauling the dewatered solids
to the disposal area. It is assumed that the municipality
will already own a dump truck that could be used for this
purpose. Therefore, it will not be necessary to include the
capital cost of the truck. An appropriate portion of the
79
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truck's maintenance and replacement costs will be included in
the operation budget.
For most applications the hyacinth basins can be sealed
with a clay liner. Under some circumstances an artifical liner
will be required to prevent seepage of the wastewater into the
the groundwater. Artifical liners are expensive, ranging from
$12 to $37 per sg m. Table 23 presents a range of costs for
artificial liners for each case at various flows.
TABLE 23. COST OF ARTIFICIAL LINER FOR A WATER HYACINTH
AQUACULTURE SYSTEM, $ MILLION, ENR CCI 3384*
Flow (cu m/day) Case 1 Case 2 Case 3
400
800
2000
4000
8000
0.072-0.22
0.144-0.44
0.36-1.1
0.72-2.2
1.44-4.4
0.024-0.075
0.048-0.15
0.12-0.38
0.24-0.75
. 0.48-1.5
0.13-0.41
0.25-0.82
0.65-2.1
1.3-4.1
2.5-8.2
* Based on $12 to $37/m2 of liner
As discussed in previous sections, aquaculture systems
located in colder climates may require greenhouses to insure
proper temperature for plant growth. The actual cost of a
greenhouse varies depending on the design, method and materials
of construction and environmental conditions. Costs of
existing greenhouses and quotes on greenhouses for systems in
the design stage range from $27 to $108 per sq m ($2.5 to $10 a
sq ft).
O&M cost estimates were developed for labor, replacement
of equipment, maintenance of equipment and fuel consumed.
The labor costs can be broken down between daily operation
and harvesting. The annual hours for labor have been estimated
by Robinson (Reference 27) for various surface areas using a
logarithmic relationship and include operation and maintenance
labor, and administration. Table 24 shows labor hours for the
three cases.
80
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TABLE 24. ANNUAL LABOR HOURS - EXCLUSIVE OF HARVESTING AND
SOLIDS DISPOSAL (REFERENCE 27)
Case 3
Flow (cu m/day)
Case 1
Case 2
400
800
2000
4000
8000
160
230
360
540
750
90
130
225
325
470
230
300
480
740
1050
The estimate of the labor demands for harvesting are for
the same harvesting system as described in the energy and
capital cost section. The equipment requires only one
operator. The unit labor demand is 290 hours per hectare per
year which includes the actual harvesting time, unloading and
transport time. The labor required by the truck driver for the
solids disposal is 10 hours per hectare per year. Therefore,
the total labor required for harvesting is 300 hours per
hectare per year. Table 25 presents the total labor required
for the harvesting and solids disposal.
TABLE 25. TOTAL ANNUAL LABOR HOURS REQUIRED FOR THE HARVESTING
AND DISPOSAL OF AQUACULTURE SYSTEM SOLIDS
Flow (cu m/day)
Case 1
400
800
2COO
4000
8000
180
360
900
1800
3600
Case 2
Case 3
72
144
360
9720
1440
330
630
1500
3300
6300
The total operation and maintenance costs include mainte-
nance of the aquaculture system harvesting equipment, solids
disposal truck, pumps, and the replacement cost of the har-
vesting equipment which has an expected life of 10 years, and
the cost of the energy expended. The unit cost of the equip-
ment maintenance is $256 per ha per year. It is assumed that
the cose of maintaining the hauling truck will be shared among
the \arious agencies in the community. The annual maintenance
cost is estimated to be 5% of the capital cost, or $1750 a
year. Pumps are assumed to have a 20 year life and an annual
maintenance cost of 5 percent of the capital cost. The annual
81
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i
*
• • 1
maintenance of the aquaculture system (e.g./ levee and piping
repairs) is estimated to be 0.5 percent of the capital earth-
work costs. In ten years and at a 7 percent annual increase,
the replacement cost of the harvesting equipment will be about
$179/000. The annual replacement cost over 20 years is $8,590.
The annual energy cost estimate includes the cost for the
energy demands described in the energy analysis, plus an
additional 10 percent for miscellaneous energy uses.
The total operation and maintenance cost for an aqua-
culture system is shown in Table 26.
TABLE 26. ANNUAL OPERATION AND MAINTENANCE COST FOR AN AQOA-
CDLTDRE SYSTEM, ENR CCI 3384
Flow (cu m/day) Case 1 Case 2 Case 3
400
800
2000
4000
8000
9 5,110
8,200
25,550
33,100
64,000
9 4,400
6,790
22,000
26,000
49,900
$ 4,050
5,790
20,250
20,500
42,930
There are 15 situations (3 different cases and 5 different
flow rates) which could be analyzed. To keep this assessment
concise, only one flow rate will be used for the 3 cases
studied for the detailed cost analysis. The methodology used
for the cost estimate can be applied for any of the flow rates
and combination of cases. A flow rate of 4000 cu m. day (1.06
mgd) has been chosen as the representative flow for small
communities, other assumptions include:
o System operating 12 months/year
o Pumping required to overcome a 3 meter static lift
o Artificial liner not required
o .Greenhouse not required
o Land costs at $3,000/ha ($l,335/acre)
o The salvage value of land is calculated by escalating
tbe purchase price by 1.806 (appreciation at a com-
pound interest rate of 3 percent/year for 20 years).
Tbe present worth of the salvage value at the end of
20 years is that value multiplied by the single pay-
62
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roent present worth factor at 7 percent for 20 years
(0.2584).
The average annual cost for Case 1, primary effluent to
secondary, is $76,100, for Case 2, secondary effluent to
advanced secondary, is $82,200, and for Case 3, .advanced
secondary effluent to AWT, is $166,800. The cost breakdowns
are presented for each case in Tables 27, 28 and 29.
83
$r
t
L
I
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TABLE 27. ESTIMATED COSTS FOR AM AQGAOJLTOPE SYSTEM, CASE 1, 4,000 CU in/day,
Bit CCI 3384
Capital Annual Present Total Average
Item O&M Worth Present Annual
•y OSM Worth '
Earthwork s 585,000 $ 2,900
Land Acquisition 18,000
Punping 82,000 4,100
Harvesting
equipment 91,000 8,590
Labor — 25,740
Dtatp truck for
solids disposal — 1,750
Misc. equipment — 1,540
Subtotal 1 776,000
costs 6 28% 217.000
Subtotal 2 993,000
Non-construction
costs 9 30% 298.000
Subtotal 3 1,291,000
Energy-
electricity 600
Energy -
gasolinb 8,100
Subtotal 4
Land Salvage
Value (subtract)
TOTAL
44,620 $ 472,700 $1,763,700 $ 166,480
7,124
103,210
7,124
103r210
1,874,000
8.400
672
9.740
176,890
.790
$1 . 865 r600 $176 .100
84
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TABLE 28. ESTIMATED COSTS FOR AN AQOACOLTORE SYSTEM, CASE 2, 4000 CU in/day,
ElitCCI 3384 v
Itero
Earthwork
Land acquisition
Punping
Harvesting
equipment
Labor
Duq> truck for
solids disposal
Hies, equipnent
Subtotal 1
Non-canponent
costs i 28%
Subtotal 2
Non-construction
costs 9301
Subtotal 3
Energy-
electricity
Energy-
gasoline
Subtotal 4
Land Salvage
Value (subtract)
TOTAL
Capital
$142,700
7,200
82,000
91,000
323,000
90.000
413,000
124.000
537,000
0
Annual Present
O&H Worth
O&N
$ 715
4,100
8,590
11,500
1,750
610
27,260 288,850
600 7,124
3,24C 41,300
0 0
Total Average
Present Annual
Worth
825,900 77,950
7,124 672
41.300 3.900
874,300 82,500
3.?4p 320
ftO^I AAA ft O^ Oftrt
i?&/J^UW T Bn V •Uw
85
-------
Bit OCX 3384
Item
Earthwork
Land acquisition
Punping
Harvesting
equipment
Labor
Dunp truck for
solids disposal
Misc. equipment
Subtotal 1
costs 9 28%
Subtotal 2
Non-construction
costs i 30%
Subtotal 3
Energy-
electricity
Energy-
gasoline
Subtotal 4
Land Salvage
Value (subtract)
TOTAL
Capital
$343,000
33,000
82,000
91,000
549,000
154.000
703,000
914,000
Annual Present
O&H worth
OfiM
$ 1,700
4,100
8,590
44,440
1,750
2,820
63,400 $671,700
600 7,124
14,850 189,300
Total Average
Present Annual
Worth
$1,585,700 $149,700
7,124 672
189,30p 17.868
1,782,100 168,240
15.400 1.450
$1.766.700 $166.800
86
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SECTION 5
COMPARISON WITH EQUIVALENT CONVENTIONAL TECHNOLOGY
COST COMPARISON
A range of average annual costs for conventional secondary
and advanced treatment systems was developed for this com-
parison by completing a present worth analysis based on the
construction and annual 0*M cost data given in the EPA I/A
Manual (Reference 125). These costs are the unit costs for
various secondary and advanced secondary treatment systems.
The cost of treating the influent prior to the secondary,
advanced secondary, or AWT process is not included since these
costs are similar for the conventional .and aquaculture systems.
The cost of the following conventional secondary treatment
systems were included in the development of the cost curves:
activated sludge (mechanical aeration, high rate diffused
aeration, and pure oxygen), trickling filters, stabilization
ponds, rotating biological contactors, and contact stabili-
zation. The cost of the following processes were used for
conventional advanced secondary and AWT cost curves: dual
media filters, activated carbon, nitrification, Phostrip, ion-
exchange, tertiary lime treatment and ferric chloride addition.
The costs for conventional technology include solids
separation and sludge disposal. The costs for aquaculture
systems include hyacinth harvesting and disposal but do not
include sludge disposal since it was assumed that sludge
disposal would not be necessary.
The range of costs are presented in two graphs. Figure 5
for secondary treatment and Figure 6 foe advanced secondary and
AWT. These figures show the average annual cost as a function
of the plant's capacity for both the conventional and aquacul-
ture systems. The aquaculture system curves are based on the
cost estimate detailed in Section 4.
The average annual cost is based on two cost components,
the capital and the annual OfcM costs. Curves for each of these
components were developed from Reference 125. Figure 7 shows
the capital cost K.S a function of plant capacity for secondary
systems, and Figure 8 for advanced and AWT systems.
87
-------
!
o
1000
600
i
CO
&
o
o
III
o
I
100
60
10
AQUACULTURE
SECONDARY
Case I
0.1
0.6 1.0
PLANT CAPACITY - MOD
10
FIGURE 6. Avaraga Annual Costs Comparison - Secondary Traatmant
-------
2000
0.5 1.0
PLANT CAPACITY - MOD
CONVENTIONAL
ADVANCED
SECONDARY
AND AWT
•••••••••• AQUACULTURE ADVANCED
SECONDARY - Cat* 2
AQUACULTURE AWT
Case 3
FIGURE 6. Average Annual Costs Comparison - Advanced Treatment.
89
-------
10
n
«.
o-
O
09
0>
O
O
Q.
O
1.0
0.5
0.1
AQUACULTURE
SECONDARY
Co»e l\
0.1
'CONVENTIONAL
SECONDARY
0.5 1.0
PLANT CAPACITY - MOD
10
FIQURE 7. Capital Coat Compariaon -Secondary Treatment.
90
-------
I
10
o
o
09
O
o
_J
I
o
1.0
0.6
0.1
0.1
0.6 1.0
PLANT CAPACITY - MOD
CONVENTIONAL
ADVANCED SECONDARY
AND AWT
—— AQUACULTURE ADVANCED SECONDARY - Casa 2
••••••••• AQUACULTURE AWT - Cat* 3
FIGURE 8. Capital Cost Comparison - Advanced Traatmant.
10
91
-------
A graph shoving the annual 06M cost as a function of plant
capacity is shown in Figure 9 for secondary systems and Figure
10 for advanced and AWT systems.
It is important to note that the costs presented are for
the construction and operation of original aquaculture systems.
Many full scale facilities such as those located in Texas
involved conversion, of existing pond systems. The construction
costs were, therefore, relatively low because the volume of
earthwork was less and much of the labor was done by city
employees. The actual construction costs for many of these
facilities, however, have not been determined by the respective
agencies.
The advanced secondary (Case 2) system with a capacity
greater than 1,890 cu m/day (0.5 mgd) is less expensive on an
average annual basis than a conventional system. The average
annual cost for other capacity and treatment levels is within
the range of the conventional system costs.
Evaluation of Figures 7 and 8 indicate that capital costs
for aguaculture advanced treatment systems, Case 2 and 3, are
competitive with the conventional system capital costs. For
secondary treatment (Case 1), the capital cost comparison is
split; aguaculture systems with capacity greater than 3,785 cu
m/day (1 mgd) are cost competitive, and capacities less than
3,785 cu m/day are more costly to construct than conventional
systems.
Review of the annual O&M cost curves (Figures 9 and 10)
indicates that for Case 1 and Case 3, advanced secondary and
AWT, the annual O&M costs are within the range of conventional
systems. For the advanced secondary aquaculture systems (Case
2), the O&M costs are less than conventional systems for plants
with greater than 1,890 cu m/day (0.5 mgd) capacity, and are
competitive with conventional systems for plants with less than
1,890 cu m/day capacity.
ENERGY COMPARISON
The energy requirements for conventional treatment systems
were determined from References 126 and 127. The conventional
secondary systems considered are activated sludge with clarifi-
cation, trickling filter, rotating biological contactors, and
contact stabilization. The conventional advanced and AWT
systems used for comparison are activated carbon, dual media
filter, nitrification, Phostrip, ion-exchange (for ammonia
removal) and ferric chloride addition. The aquaculture
system's demands are based on the assumptions and discussion
92
-------
1000
500
o
v
i
co 100
CO
O
o
1 50
z
10
CONVENTIONAL
SECONDARY^
rf*j>* ','$»$ te&fci. "•
^^&!^«.3&&
"Zsl** .. .1.' •* ** I 3.l(~ U .tl.lf.. !,..«' I J. , it X" J "• _ >
s.-ov?
•-..'.'i-*.,^,?^,:
-AQUACULTURE
SECONDARY
Cote I
0.1
0.5 1.0
PLANT CAPACITY - MOD
10
FIGURE 9. Annual O&M Cost Comparison - Secondary Treatment.
-------
1COO
0.1
0.5 1.0
PLANT CAPACITY - MOD
10
; £t v.
CONVENTIONAL
ADVANCED SECONDARY
AND AWT
—— AQUACULTURE ADVANCED SECONDARY - Case 2
AQUACULTURE AWT - Cat* 3
FIGURE 10. Annual OftM Coat Comparison - Advanced Treatment.
94
-------
^k^
presenteVin Section 4. These energy demands include solids
separation and disposal.
As with the cost comparison, the conventional system
energy demands have been compared with the aguaculture system
demands as a function of plant capacity as shown in Figure 11
and 12. Since the harvesting process consumes energy in the
form of gasoline, the comparison between the aguaculture and
conventional plants is made in Btu's. In converting the
electrical kwh demand into equivalent Btu's, a conversion effi-
ciency of 33 percent was used.
Figure 11 shows that secondary treatment using an agua-
culture system (Case 1) consumes less energy than a conven-
tional system. Estimated savings for secondary systems are
shown in Table 30. Since the energy demand for the conven-
tional system is presented as a range in Figure 11, the mid-
point energy value for the selected flow rates is used for the
comparison. As Table 30 shows annual savings of 74 to 85
percent.
Conventional and aguaculture advanced secondary and AWT
are compared in Figure 12. Both advanced secondary and AWT are
within the range developed for conventional advanced secondary
and AWT.
The energy demands of the aguaculture systems are
primarily due to the harvesting reguirements (440 wet metric
tons/ha/year) and hyacinth disposal. If the harvesting
reguirements of a specific system can be reduced, the energy
costs would be reduced and may compare more favorably with that
of.the conventional systems.
TABLE 30. COMPARISON OF AQDACOLTORB AND CONVENTIONAL SECONDARY
SYSTEM ANNUAL ENERGY REQUIREMENTS (BtU/yr)
Flow Rates cu. m./day
Treatment Type
Conventional
Aguaculture
Savings
*
400
3.91xl08
8.14X107
3.10xl08
79%
2000
1.56X109
4.07X108
1.15X109
74%
4000
3.19X109
8.14xl08
2.38xl09
74%
8000
1.07X1010'
1.63xl09
9.07X109
85%
95
-------
50,000
Conventional
Aquaeuttura
Secondary
Caaa 1
6.0 10.0
PLANT CAPACITY - MOD
FIGURE 11. Comparison of Enargy Demanda - Secondary Treatment.
96
-------
10,000
5.000
X
1.000
s 600
ui
a:
o
IU
a
>
o
1C
UI
UI
Conventional
Advancad Secondary
and AWT
Aquacultura
••«••••' Advanotd Secondary
Caaa 2
Aquacultura AWT
100
O.S 1.0
PLANT CAPACITY - MOD
FIGURE 12. Compariaon of Enargy Damanda - Advanead Traatmant.
-------
SECTION 6
NATIONAL IMPACT ASSESSMENT
POTENTIAL MARKET
Aquaculture systems are usually United to suburban and
rural communities because of the land area requirements.
Theoretically, an aquaculture system can be designed for any
capacity* but because the system is land intensive, the cost
and availability of land are limiting factors for application
in an urban setting.
The plants and animals that inhabit aquaculture systems
are sensitive to temperature. Therefore, climftte is a major
factor in determining the potential market for aquaculture
systems. Each of the aquaculture plant-and animal species have
their own optimum temperature range for growth. The
temperature range given in the literature for the various
species is for water temperature. Correlating the water
temperature to the air temperature is a site-specific process,
dependent on the size and depth of the body of water. It is
difficult to determine, on a national basis, the geographical
areas in which certain plants or animals would survive in a
natural environment for a given period of time. However, a
design manual on hyacinth systems (Reference 43) recommends a
temperature range based on air temperature. It is postulated
that water hyacinths would thrive in an environment where the
average air temperature ranges from 4.4 to 35°C (40 to 95°P).
Prom this guideline a rough division can be made of where an
uncovered hyacinth system would be feasible. Tear-round
hyacinth growth in the natural environment is restricted to
southern Plorida and southern Texas.
An aquaculture system may also be installed for seasonal
use such as for nutrient removal during the spring and summer
months* Aquaculture systems may also be covered to provide a
more controlled environment. However, it is likely that a
system that requires the additional cost of a greenhouse
structure will not be cost-effective based on the previous cost
analysis. Therefore, only non-covered systems will be
considered in this assessment. The potential market will be
restricted to regions that have a minimum of six continuous
months with a maximum average monthly tempertnre of 35°C <95°P)
and a minimum average monthly temperature of 4.4°C (40°P).
98
-------
figure 13 locates this region on a nap of the continental
United States. This nap is based on the temperatures reported
in Reference 128.
The EPA's 1978 Needs Survey (Reference 129) estimated (for
various states, flows, and treatment levels), the number of
wastevater treatment plants that will be required to be con-
structed during the years 1978 to 2000. The temperature
bounoary division line (on Figure 13) crosses through the
middle of some states. In tabulating the number of plants that
constitute the potential market, certain assumptions were made.
Where more than half of the area of a state is not included in
the correct temperature xone, its number of plants were not
included in the count. All plants were included for states
with more than half of their boundary in the proper temperature
growth zone.
Although aquaculture systems have been designed to treat
raw sewage, it has been recommended that primary effluent be
the minimum aquaculture influent quality. The Needs Survey
gives the estimated number of secondary treatment plants, and
advanced secondary and tertiary facilties that will be
constructed during the years 1978 to 2000. The number of
plants within the climate and capacity limitations are pre-
sented in Table 31.
TABLE 31. ESTIMATED NUMBER OP TREATMENT PLANTS TO BE CON-
STRUCTED DURING THE YEARS 1978 TO 2000 WITHIN
CLIMATIC ZONES PAVORABLE TO WATER HYACINTHS
(Reference 129)
Total Projected Plow (n3/day)
Level of
Treatment 1-400 401-1900 1910-4000 4001-7570 Total
Secondary 2146 842 128 35 3151
Advanced ifitn 595 107 us 2421
Total 3753 1437 235 150 5575
COST AND ENERGY IMPACTS
As discussed in Section 4, no monetary savings would be
realised by using an aquaculture system rather than a conven-
tional system for facilities with capacity of less than 18*900
en m/day (5 mgd). All the aquaculture systems are expected to
99
-------
-------
be cost competitive with conventional plants, except for
secondary aquaculture systems with flows greater than 5680 cu
a/day (1.5 mgd). Therefore, the national impact of using
advanced secondary and AWT aquaculture systems would not in-
volve an increase or decrease in the funds expected to be spent
on wastewater treatment facilities. An increase in spending is
anticipated if secondary aquaculture systems with flows greater
than 5680 cu m/day (1.5 mgd) were implemented. Since there are
only 35 secondary treatment plants with flow greater than 5,680
cu m/day (1.5 mgd) expected to be built between 1978 and 2000
within climatic zones favorable to water hyacinths, the
expected increase in spending over the next 20 years is not
significant.
As discussed in Section 5, the use of aquaculture systems
for secondary treatment will save energy as compared to con-
ventional systems. However, based on the assumption used in
this analysis aquaculture systems for advanced secondary and
ANT could use more energy than some conventional
Based on the data from the Heeds Survey and the energy
comparison graphs (Figure 11 and 12), Table 32 indicates the
estimated energy savings. The energy demands of conventional
facilities were derived from the appropriate curve on Figures
11 and 12, at the higher end of the flow range (e.g., at 400 cu
m/day for the 0 to 400 cu m/day range) and at the mid-point of
the cost range*
The estimated savings from the use of aquaculture systems
for 10 percent of the new secondary treatment plants (under
7575 cu m/day) is 2.34x10** Btu/year. The energy savings
achieved by using aquaculture systems for 10 percent of
advanced treatment (plants under 7575 cu m/day) is 2.86X1011
Btu/year.
PERSPECTIVE
The 1978 Heeds Survey (Reference 129) estimates that about
914 billion would be spent over the next 20 years in the United
States for secondary treatment facilities including new con-
struction, and enlarging and upgrading existing plants. For
plants with capacity less than 8,000 cu m/day the estimated
cost is about 93.5 billion. The impact of the potential in-
crease in spending from installing aqnaculture systems for
secondary treatment over the next 20 years should be minimal.
101
-------
TABLE 32. ESTIMATED AHMDAL ENERGY DEMANDS FOR THE ANTICIPATED
TREATMENT PLANTS, 1978-2000, BTD/YEAR
Level of Total Projected Flow (cu. m./day)
Treatment 1-400 401-1900 1910-4000 4001-7570 Total
Secondary
3.91x10* 1.56x10* 3.19X1Q9
8.54x10 k° 1.31x10" 4.15X1010
Conventional
Per plant
10% Total US
Aqua culture
CCase 1)
Per plant .. ..
10% Total DS 1.75xl010 3.42X1010
1.07x10}J ..
4.28xl010 S.OlxlO11
8.14x10. 4.07x10?
8.14x10*
1.06x?.010
Savings
(Convent.-
Aquaculture)
6.79xl010 9.68X1010 3.09xl010
1.63x10J ,.
6.52xl09 6.75X1010
3.63X1010 2.34X1011
78%
Advanced Secondary and AWT
Conventional
Per plant 7.75X107,,. 3.85x10* 8.13x10*
10% Total DS 1.25xl010 2.31xl010 8.94xl09
Aquaculture
(Case 2)
Per plant 4.17xl07a 2.09x10* 4.17x10*
10% Total DS 6.71xl09 1.25xl010 4.59xl09
Savings
(Convene.- 5.59xl09 l.OSxlO10 4.35xlC9
Aquaculture)
1.52xl09A ...
1.82xl010 6.27xl010
8.34x10*
l.OOxlO10 3.38xl010
8.20X109 2.06X1010
46%
For advanced secondary tnataent and AWT facilities '{in-
cluding new construction, and enlarging and upgrading ««istin£
plants), the Keeds Survey estimate* that »20 billion will be
spent over the next 20 years. For plants with flows less *h*n
8,000 cu »/day, the estimate is about >4.9 billion, since the
cost of advanced systear is comparable with conventional
system, there should not be any inpact on the amount of funds
required for advanced treatment of plants with flows less than
8,000 cu s^day.
102
-------
Bnargy
AS reported in the EPA publication Energy Conservation in
Municipal Waatewater Treatment (Reference 130), the 1990 esti-
mated energy consumption at public!v owned treatment works for
secondary treatment is 216.51X101' Btu/year and 40.40x10-"
Btu/year for tertiary treatment. The 1990 national energy use
is estimated to be 1145xl015 Btu/year. The saving? realized by
using aquaculture systems for secondary and advanced treatment
systems are insignificant when compared to the national energy
budget.
MARKETABILITY
As previously discussed, the potential market for aquacul-
ture systems is limited in relation to the market for all
wastewater treatment facilities in the United states. This
market is generally limited to suburban and rural communities
that have large areas of reasonably priced land available and
wastewater flows less than 8,000 cu m/day.
The mirketability of aquaculture requires that a community
select an aquaculture system over another system. However, a
certain level of risk is associated with the selection of an
aquaculture system. The risks are due to aquaculture systems
being an unproven wastewater treatment technology, and because
they are natural systems dependent on environmental conditions.
The risk is reduced with each aquaculture system implemented.
As more performance data are developed, the more refined and
reliable the design criteria become. Natural systems have the
added drawback that direct control over the process is limited.
A community may justify the risk of selecting aquaculture
systems by arguing that the risks involved with conventional
plants are similar. Many existing conventional treatment
systems have not met effluent discharge requirements and are
experiencing operational problems.
The risks involved with aquaculture systems vary. There
are two possible results in situations where aquaculture
systems are installed and fail to perform. First, the aquacul-
ture system may be abandoned and a new treatment system
installed, in this case about 3 to 7 percent of the capital
cost aay be regained by selling the land. Salvaging equipment
and materials may also reduce the losses. About 28 to 45
percent of the capital cost is for earthwork, which cannot be
reclaimed and would have to be taken as a direct loss. The
second possible result is that the new treatment process may
incorporate the aquaculture system into its design.
103
-------
SECTION 7
LIST OP REFERENCES AND CONTACTS
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Wiley t Sons/ New York, 868 p.
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3. United States Environmental Protection Agency MERL, 1982.
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4. Allen, G.B., 1969. A Preliminary Bibliography on the
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5. Allen, 6.B., 1972. "The Constructive Use of Sewage, with
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104
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10. Duffer, W.R. and J.E. Moyer, 1978. Municipal Wastewater
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PJL&£££illllfl.&, University of California Davis,
September 11-12, 1979. U.S. Environmental Protection
Agency, Wash., D.C. (EPA 430/9-80-006, HCD-67), 485
P-
12. S.C. Reed and Bastian R.K. (Eds.), 1980. Aguaeulture
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Water Resources Control Board, Sacramento,
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105
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18. Stephenson, M., G. Turner, P. Pope, A. Knight, and G.
Tchobanoglous, 1980. The Use and Potential of
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1980. The pse and Potential of Aquatic Species fqr
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