United States
Environmental Protection
Agency
Office of Water Regulations
and Standards
Criteria and Standards
Washington, DC 20460
May 1982
Water
&EPA
Benefits and Implementation
Potential of Wastewater
Aquaculture
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Benefits and Implementation Potential of
Wastewater Aquaculture
Contract No. 68-01-6232
Prepared for
Criteria and Standards Division
Office of Water Regulation and Standards
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, B.C. 20460
January 1982
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ABSTRACT
The use of aquaculture as a wastewater treatment technology is a relatively
recent development.' This study was conducted to assess why aquaculture is
not being more widely used to treat industrial, agricultural, and municipal
waste waters. Wastewaters amenable to aquaculture treatment are inventoried
and constraints which are limiting to more widespread application of aquaculture
technology are assessed. The report concludes that aquaculture is a viable
technology which can be used to treat many biologically treatable wastewaters.
Potential benefits cannot be fully realized under current regulatory restrictions
and technological constraints. The study suggests that wider dissemination of
technical information, coordinated efforts to reconsider regulations, and
additional research will benefit future applications of this technology.
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ACKNOWLEDGEMENTS
The cooperation of William C. Shilling, Lowell Keup, Robert Bastian, W. Ray
Dinges, Henry R. Thacker, B.C. VVolverton, William Cartter, George Kohut,
Ted McKim, Mark Evans, Scott Henderson, and Fred Wheaton who assisted in
providing information, guidance and review for this document is gratefully
acknowledged.
The following individuals assisted in preparation of this document: Dennis M.
Kamber, Kenneth A. Hosto, James S. Whang, Eileen K. Straughan, Edwin F.
Earth, 111, and Kathy S. Lentell.
Xll
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TABLE OF CONTENTS
age
Abstract ii
Acknowledgements iii
Tables " . . . . . v
Figures vii
1. INTRODUCTION AND SUMMARY 1-1
1.0 Introduction . 1-1
1.1 Summary 1-2
2. \VASTEWATER AQUACULTURE POLLUTANT
REMOVAL MECHANISMS AND
TREATMENT SYSTEM DESCRIPTIONS 2-1
2.0 Introduction 2-1
2.1 Removal Mechanisms 2-1
2.2 Existing Wastewater Aquaculture
Facilities 2-12
References 2-41
3. AMENABILITY OF WASTEWATERS TO
AQUACULTURE APPLICATIONS 3-1
3.0 Introduction 3-1
3.1 Amenability Assessment Methodology 3-1
References 3-14
4. GEOGRAPHICAL VARIABLES WHICH AFFECT UTILIZATION
OF AQUACULTURE TECHNOLOGIES 4-1
4.0 General 4-1
4.1 Climatological Variables 4-1
4.2 Hydrogeological Variables 4-8
4.3 Summary 4-12
References 4-13
5. NUTRITIONAL AND FINANCIAL DETERRENTS TO
WASTEWATER AQUACULTURE 5-1
5.0 General 5-1
5.1 Clean Water Act of 1977
(P.L. 95-217) 5-1
5.2 National Aquaculture Act of 1980
(P.L. 96-362) 5-3
5.3 Food and Drug Cosmetic Act (FDCA) 5-3
5.4 Sludge Management Regulations 5-4
5.5 Wetlands Policies and Other Land
Use Restrictions 5-5
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5.fi Species Restrictions 5-6
5.7 Land and Water Use Restrictions 5-6
5.8 Financial Considerations Influencing
Wastewater Aquaculture Development 5-7
5.9 Summary 5-8
References . 5-10
6. DESIGN AND OPERATION OF AQUACULTURE
TREATMENT FACILITIES 6-1
6.0 Introduction 6-1
6.1 Design Considerations 6-2
6.2 Summary 6-18
References 6-20
7. ECONOMICS OF WASTEWATER AQUACULTURE
COMPARED TO CONVENTIONAL
TREATMENT TECHNOLOGIES 7-1
7.0 Introduction 7-1
7.1 Case Studies 7-5
7.2 Summary 7-19
References 7-21
8. BY-PRODUCTS DERIVED FROM
WASTEWATER AQUACULTURE 8-1
8.0 General 8-1
8.1 Potential Uses of Aquaculture
Products Derived from Wastewater 8-1
8.2 Food for Direct Human Consumption 8-2
8.3 Soil Amendments, Fertilizers
and Compost 8-7
8.4 Fiber 8-9
8.5 Biogas Production 8-10
8.6 Feeds and Feed Supplements 8-11
8.7 Harvesting and Processing Wastewater
Aquaculture Biomass 8-14
8.8 Harvesting and Processing Aquatic Animals .... 8-19
References 8-20
LIST OF TABLES AND FIGURES
Tables
2.1 Relative Uptake Efficiency of Waste
Contaminants by Aquatic Plants in Batch
Study: 28-Day Detention Time 2-11
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2.2 Removal of Trace Conventional Pollutants
by Water Hyacinth and Bulrush 2-13
2.3 Existing Plant Wastevvater Aquatic
Processing Units (APU) 2-15
2.4 Abandoned Plant APU's 2-17
2.5 Performance of Duckweed Aquatic
Treatment Systems 2-23
2.6 Polyculture (combined) APU Research
Projects 2-27
2.7 Level of Performance of Combined
Aquaculture Treatment Systems 2-29
2.8 Existing Natural Wetlands Treatment Sites 2-30
2.9 Existing Artificial Wetlands APU's 2-34
2.10 Abandoned Artificial Wetlands APU's 2-36
2.11 Level of Performance of Reeds/Bulrushes
Treatment System MPI System at Laguna Niguel,
California 2-40
3.1 Significant Pollutants of Major
Industrial Categories 3-3
3.2 Wastewater Amenability for Aquaculture Uses 3-7
4.1 Climatological and Hydrogeological Variables
Affecting Aquaculture 4-2
4.2 Range of Probable Yield of Algae from A
Properly Designed Algae Aquaculture System 4-4
4.3 Thermal Aquaculture Facilities 4-6
6.1 Proposed Design Criteria for Aquaculture
Treatment Systems 6-9
7.1 Total Annual Energy for Typical 1 MGD
System 7-2
7.2 Examples of Typical Land Requirements, Total
Construction Costs, Labor Requirements,
Parts and Supply Costs, and Total Energy
Requirements for Natural Treatment Systems,
Activated Sludge and Trickling Filter Systems .... 7-4
VI
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7.3 Cost Comparison Between Aquaculture and
Conventional Treatment Alternative -
Case Study No. 1 7-7
7.4 Cost Comparison Between Aquaculture and
Conventional Treatment Alternative -
Case Study No. 2 7-8
7.5 Cost Comparison Between Aquaculture and
Conventional Technology - Case Study No. 3 7-9
7.6 Cost Comparison Between Aquaculture and
Conventional Treatment Alternatives -
Case Study No. 4 7-10
7.7 Cost Comparison Between Aquaculture and
Conventional Treatment Alternatives -
Case Study No. 5 7-12
7.8 Cost Comparison Between Aquaculture and
Conventional Treatment Alternatives -
Case Study No. 6 7-13
7.9 Cost Comparison Between Aquaculture and
Conventional Treatment Alternatives -
Case Study No. 7 7-14
7.10 Estimated Costs for Selected Alternatives -
Hypothetical Case Study 7-17
8.1 Concentration of Mineral Feed Nutrient
Elements for Water Hyacinths 8-13
8.2 Nutritional Analysis of Wastewater Grown
Spirodela obligorhiza in Comparison with
Several Animal Feeds 8-15
8.3 Comparison of Sewage Lagoon Biomass Vitamin
Content with Other Feeds 8-16
Figures Page
2.1 Possible Liquid Process Trains for
Combined Aquaculture Treatment Systems 2-26
2.2 Removal Performance for Artificial
Wetlands Aquaculture System,
Neshaminy Falls, PA
(April 1, 1980-September 1981) 2-37
6.1 Simplified Flow Diagram of Typical
Aquaculture Treatment Systems 6-5
8.1 Food Chain Polyculture 8-5
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CHAPTER 1
INTRODUCTION AND SUMMARY
1.0 INTRODUCTION
Aquaculture can be defined as the mass culture of higher forms of aquatic
plants and animals. Under the National Aquaculture Act of 1980 and Draft
National Aquaculture Plan (1981), the Federal Government has recognized that
there is a substantial potential for providing food, employment, recreation and
other values to the public through aquaculture. While the major thrust of this
legislation is to encourage aquaculture as a method of farming to produce food
and fiber, one of the other values of aquaculture to the public is to provide
treatment of certain types of wastewaters and beneficial recycling of wastes.
The U.S. Environmental Protection Agency (EPA), under guidance for its
municipal treatment works construction grants program (40CFR35.908) has made
it policy to encourage and assist in development of aquaculture technology for
wastewater treatment.
While far from applicable to all wastewater treatment problems, aquaculture can
be an attractive alternative in certain instances to more mechanized, chemical,
and energy consumptive conventional treatment processes. Much of the
attractiveness of wastewater aquaculture stems from the reliance of such
systems on naturally occurring processes to remove pollutants from wastewaters.
Whereas the objective of much of current aquaculture technology is to produce a
marketable biomass crop, the objective of wastewater aquaculture is to produce
clean water. The biomass produced by a wastewater aquaculture facility is only
of secondary importance. If the biomass by-products from a wastewater
aquaculture facility can be marketed and sold, the revenue can be used to help
offset wastewater treatment costs.
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Even though the Clean Water Act encourages recycling and beneficial re-use of
waste materials, the wastewater treatment and aquaculture industries have only
made limited advancement in this area. In keeping with Federal policies and
plans to encourage aquaculture, the U.S. EPA has undertaken this study to
assess why aquaculture is not being more widely used to treat industrial,
agricultural and municipal wastewaters. This assessment had as its major
objectives the development of an inventory of wastewaters amenable to
aquaculture treatment, and an assessment of the constraints which are limiting
to more widespread application of wastewater aquaculture processes as
alternatives to conventional wastewater treatment.
This study has attempted to analyze the benefits and constraints of wastewater
aquaculture technology in order to provide information and recommendations that
may further the development of this technology. In order to assess the current
status of wastewater aquaculture, the following questions were addressed:
What are the various components of wastewater aquaculture systems and
what pollutant removal mechanisms can be identified?
What types of wastewater sources are potentially amenable to aquaculture
treatment?
What geographical and climatological constraints limit the location of
particular wastewater aquaculture systems?
What types of institutional and financial considerations constrain or
encourage application of wastewater aquaculture technologies?
Is there sufficient reliable design information available to engineers for use
in designing wastewater aquaculture systems with confidence?
How do wastewater aquaculture systems compare economically to
equivalently performing conventional systems?
What factors influence by-product harvesting, processing and marketing?
1.1 Summary
This assessment of wastewater aquaculture has led to the following conclusions:
1. Aquaculture treatment processes have been, and continue to be
demonstrated capable of secondary, and advanced treatment (nutrient
removal) of municipal and certain industrial and agricultural wastewaters.
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2. Aquaculture treatment technologies have been applied with a certain degree
of success to the treatment of industrial wastewaters such as petroleum
refinery wastewater, paper manufacturing wastewater, mine tailings
wastewater containing radionuclei, dairy wastes, swine wastes and others.
In controlled, experimental environments, aquaculture treatment systems,
especially those using aquatic plants, have been demonstrated capable of
removing certain refractory organics, heavy metals, and other non-metal
elements including boron and arsenic. Aquaculture treatment systems
should at least be capable of treating agricultural and industrial
wastewaters from sources such as the food processing industry, paper
manufacturing industries, beverage industries, meat packing, feedlots and
other biologically treatable organic waste sources.
3. Wastewater aquaculture has been demonstrated cost-effective for certain
applications. The technology offers potential economic benefits due to
low-energy and chemical use compared to conventional treatment processes.
While the cost-effectiveness of wastewater aquaculture is not dependent on
sale of by-products, it is evident that by-product sale can greatly improve
the cost-effectiveness and attractiveness of wastewater aquaculture.
4. The potential economic benefits, however, cannot be fully realized under
current Federal and State laws which severely restrict the marketability of
wastewater aquaculture by-products. Further demonstration of the safety
of wastewater aquaculture by-products from particular types of wastewater
is necessary before legal restrictions' can be re-evaluated for possible
relaxation.
5. There are risks associated with implementation of conventional treatment
technologies which stem from design and operational problems.
Aquaculture technologies face comparable risks. With proper application of
the technology, proper design and proper management wastewater
aquaculture can function at least on a par with conventional technologies
and in some respects is superior.
6. One of the greatest potential applications of wastewater aquaculture is as a
unit process within more conventional process trains to renovate secondary
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treated effluent. Wastewater aquaculture has comparatively large land
requirements and is a relatively low-energy, naturally based technology.
Consequently, the use of wastewater aquaculture treatment probably has
its greatest applicability in rural areas.
7. Aquaculture treatment systems are both land and water-based as compared
to land treatment systems which is only land based. Consequently,
aquaculture treatment systems, in most cases, dictate less of a land
requirement compared to land treatment systems. Aquaculture treatment
technologies, if properly applied, designed, and managed, can prove to be
a cost-effective and viable alternative to land treatment technologies among
other innovative/alternative wastewater technologies.
8. While research during the last decade has greatly expanded the
state-of-the knowledge about aquaculture treatment systems, in order to
optimize performance and gain wider application and acceptance of
aquaculture treatment technologies, there are a number of technical
constraints which need to be addressed. These research needs include:
Development of procedures that can be used by planners and
engineers for screening, selecting, and adopting candidate aquatic
species for a particular aquaculture treatment problem.
Better understanding and quantification of the removal mechanisms
and rates of removal which occur in aquaculture treatment systems.
Better understanding of the dynamic nature of aquatic process units
(APUs) including the effects of environmental or climatic factors on
removal mechanisms.
The threshold concentrations of various pollutants tolerable by
various aquatic species.
The optimal environmental conditions for growing various aquatic
species, and cost-effective techniques for achieving and maintaining
these conditions.
Better understanding of various wastewaters and levels of
pretreatment requirements prior to treatment in aquatic processing
units (APUs).
Development of documented procedures for starting up, operating,
and maintaining an APU and better understanding of APU
controllability and strategies for process control.
1-4
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Further documentation of the role of biomass harvesting (criteria,
timing, and frequency) for various types of aquatic process units.
Ability to obtain accurate predictive mathematical models for various
types of APUs by considering their dynamic and kinetic
characteristics.
Wider dissemination of available technical information regarding
wastewater aquaculture applications, design, construction, operation
and associated environmental effects.
If these technological constraints and legal and financial restraints on
wastewater aquaculture are removed, then this technology can prove to be
a viable alternative to conventional wastewater technologies.
9. The aforementioned constraints can be effectively resolved or eliminated by
initiating the following activities:
Wider dissemination of technical information regarding aquaculture
treatment technologies using public media, e.g.; technical seminars;
technical conferences; news releases; audio-visual materials;
preparation and distribution of planning and design handbooks,
documents, manuals, etc.; and publication and distribution of cost
data related to aquaculture treatment system design, construction,
and management.
Coordinated efforts among affected Federal agencies including EPA,
Department of Commerce, Food and Drug Administration, Department
of Agriculture, Department of Interior to examine and revise existing
regulations affecting cost-effective applications of wastewater
aquaculture technologies with a common objective toward greater
beneficial, but controlled, use of wastewater aquaculture products or
by-products.
Sponsorship of research specifically designed to promote better
understanding and solutions of the aforementioned technical problems.
1-5
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CHAPTER 2
WASTEWATER AQUACULTURE POLLUTANT
REMOVAL MECHANISMS AND TREATMENT SYSTEM DESCRIPTIONS
2.0 INTRODUCTION
Wastewater aquaculture is a broad category of wastewater treatment methods
that use aquatic ecosystems to accomplish wastewater renovation. An
aquaculture-based wastewater treatment system may contain a series of aquatic
ecosystems or aquatic processing units (APUs) linked together to provide
primary, secondary or tertiary treatment, or may combine conventional and
aquaculture technologies by using an APU to accomplish a specific objective, for
example; nutrient removal. Due to the variety in aquatic species and system
alternatives possible in wastewater aquaculture technology, an assessment of
why the technology is not more widespread must necessarily include a
description of each type of system, and an inventory of wastewater facilities
using each type of aquaculture system. The inventory of facilities included in
this chapter contains presently operating facilities and identifiable non-operative
facilities that were either pilot, demonstration or research-oriented projects, or
systems that failed due to various reasons.
Prior to a discussion of the different types of wastewater aquaculture systems,
it is necessary to provide a general understanding of the type of treatment and
pollutant removal mechanisms characteristic of aquatic treatment systems.
Pollutant removal mechanisms active in wastewater aquaculture systems are of
particular interest in determining amenability of various wastewaters to
treatment, and in the optimal design and operation of aquaculture treatment
systems.
2.1 Removal Mechanisms
2-1
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There are a number of removal mechanisms occurring simultaneously and
sequentially in an aquaculture treatment system. The objective of much of the
past and on-going aquaculture research and demonstration has been to
recognize and quantify these removal mechanisms. The major removal
mechanisms include sedimentation, coagulation, adsorption, filtration,
precipitation, oxidation, reduction, bacterial metabolism, plant absorption, and
animal metabolism. Other removal mechanisms may include ion exchange,
extraction, stripping, etc. For a given pollutant, certain removal mechanisms
may dominate in an aquaculture treatment system, depending on its design and
operation conditions. The mechanisms, by which BOD, suspended solids,
nitrogen, phosphorus, heavy metals, refractory organics, and pathogens are
removed in aquaculture treatment systems, are discussed in the following
sections.
2.1.1 BOD Removal
Biochemical oxygen demands (BOD) in a wastewater generally can be separated
into two parts; soluble BCD and suspended BOD. Some of the removal
mechanisms for suspended BOD are characteristically different from those for
soluble BOD. In an aquaculture treatment system, suspended BOD is first
removed primarily by sedimentation, filtration, coagulation, and precipitation
and secondarily by absorption through floral and faunal metabolism and
catabolism. The suspended BOD is then biodegraded by microorganisms to
intermediate metabolites which generally become part of the biomass and soluble
BOD within an aquaculture treatment system. The roots and stems of plants in
an aquaculture treatment system serve as a filtering and adsorptive media and
/2)
play an important role in removing suspended BOD. ' Certain fractions of
suspended BOD including bacterial cells and plant material are refractory and
become part of the bottom sludge.
Soluble BOD, either originally contained in the wastewater, or present as a
result of conversion of suspended BOD, is biologically oxidized first to
intermediate substances and eventually to carbon dioxide and water by bacterial
enzymatic or metabolic reactions. Portions of the soluble BOD become
incorporated into the microbial mass. In an aquaculture treatment system,
aerobic bacteria are either suspended in the water column or attached to the
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roots and stems of aquatic plants, and anaerobic bacteria are generally
associated with sludge particles at the bottom sediment. Bacteria attached to
plant roots and stems are considered most productive in terms of removal of
soluble BOD.
Therefore, the removal mechanisms of suspended and soluble BOD in an
aquaculture treatment system are very similar to those in a conventional aerobic
or facultative stabilization lagoon. In a conventional aerobic or facultative
stabilization lagoon, removal of biomass from the system which is normally in the
form of suspended algae, is rather difficult due to smaller particle sizes, and
therefore is seldom practiced. In an aquaculture treatment system, removal of
biomass (consisting of primarily carbonaceous compounds) can be readily
accomplished by harvesting larger sized plants and/or animals. The refractory
fraction of the biomass will become part of the bottom sludge and only removed
through dredging.
Because of large populations of aquatic species in an aquaculture treatment
system, the emission of extracellular organic compounds by plants, excretion of
organic waste by aquatic animals, and dissolution of intermediate organic
metabolites resulting from biological digestion of bottom sediments cannot be
neglected. If growth and accumulation of aquatic species is not controlled by
periodic harvest, an aquaculture treatment system may reach an equilibrium
state, beyond which BOD removal efficiency approximates leaching of soluble
and colloidal BOD. This situation is highly variable and greatly influenced by
type of aquatic species used and amount of sludge accumulated in the system.
Maintenance of an aquaculture treatment system to contain optimal biomass at a
high productivity stage by proper harvest is the key to maximizing BOD
removal.
2.1.2 Removal of Suspended Solids
Suspended solids in a wastewater consist of settleable and non-settleable solids.
Settleable solids can be removed by sedimentation and filtration in an
aquaculture treatment system.
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Non-settleable solids, in the colloidal size range, are removed from the water
column by attaching to larger particles and plant roots through flocculation and
coagulation. Non-colloidal and non-settleable solids are removed by flocculation,
coagulation, adsorption, and filtration, and then sedimentation.
Similar to BOD, suspended solids may re-form in pond-type aquaculture
treatment systems as a result of (1) algal growth, (2) decay of aquatic plant
matter, and (3) growth and die-off of bacterial mass. Floating plant species
such as duckweed or water hyacinth, and rooted emergent plant species, such
as bulrushes or reeds have been shown to be beneficial in shading the surface
of aquaculture treatment ponds and reducing the generation of algal suspended
solids. Suspended solids production as a result of aquatic plant decay can be
controlled by periodic harvesting. Harvesting may not be practical, however,
for certain aquaculture treatment systems, especially those based on natural
wetlands.
2.1.3 Removal of Nitrogeneous Compounds
Among the nitrogeneous compounds which are frequently present in
wastewaters, ammonia, total Kjeldahl nitrogen (TKN), nitrite, and nitrate are
commonly measured as indicators for removal efficiencies of nitrogen in a
treatment system. Nitrogen removal mechanisms which occur in an aquaculture
treatment system are:
coagulation and sedimentation of nitrogeneous organic particles;
biological digestion of organic nitrogen compounds and conversion to
ammonia, nitrite, or nitrate;
conversion of ammonia or TKN materials into nitrate by bacterial
nitrification process involving primarily nitrifying aerobes such as
nitrosomonas and nitrobacter;
uptake of nitrate-nitrogen, or in some cases ammonia-nitrogen, by
aquatic plants;
engulfing and metabolism of organic nitrogen particles by aquatic
animals;
conversion of nitrate to nitrogen gas by biological denitrification
involving denitrifying bacteria.
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Storage of nitrogeneous refractory materials in the bottom sludge.
The above removal mechanisms are highly dependent on air and water
temperature and may practically cease to function during cold weather periods.
In general, microbial nitrification and denitrification predominate over other
nitrogen removal mechanisms.
Aquatic plants and animals may emit or excrete nitrogeneous compounds such as
intermediate metabolites, urea, or nitrogen-containing fecal matter back into the
treated water in an aquaculture treatment system. Die-off and decay of dead
tissue and bacterial cells can also re-introduce nitrogen loads back into an
aquaculture treatment system. It should be noted that nitrogen removal and
production mechanisms occur sequentially and simultaneously at varying rates in
an aquaculture treatment system. The reaction rates are influenced by type
and population of aquatic species, pH, temperature, energy and nitrogen input
to the system, and to a lesser extent by the other environmental variables
discussed in Chapter 4. Some of the removal mechanisms can be enhanced
artificially by construction of greenhouses over the aquaculture systems to
maintain temperatures during cold weather months which are more favorable to
active growth of aquatic plants and animals. Another artificial enhancement
method can be use of thermal effluent to provide heat supplemental to
aquaculture treatment systems during low temperature periods.
In summary, the most important method of achieving maximum nitrogen removal
efficiency is to maintain an optimal balance of energy (e.g., carbon source,
heat, etc.) and nitrogen within a system by proper harvesting of the aquatic
plants and animals. Periodic harvest reduces or eliminates net accumulation of
dead and living biomass including plant and animal tissues and microbial cells
within the system; minimizes breakthrough of nitrogenous compounds; and helps
promote maximum nitrogen removal efficiencies. Conventional treatment lagoons
usually lack practical harvest mechanisms and breakthrough of nitrogeneous
compounds is generally inevitable. This is the characteristic difference between
aquaculture treatment systems and conventional treatment lagoons with regard to
nitrogen removal.
2.1.4 Removal of Phosphorus
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Phosphorus, like nitrogen, is a macro nutrient to aquatic species up to certain
concentrations. Aquatic plants can incorporate phosphorus through their
metabolic reactions. Typical domestic wastewater and certain industrial
wastewaters contain phosphorus in excess of the normal composition of living
matter which has a carbon-nitrogen-phosphorus ratio of 100:5:1. For
phosphorus-enriched wastewaters, plant and microbial uptake of phosphorus can
only account for part of the total phosphorus removal in an aquaculture
treatment system and harvesting of aquatic species from an aquaculture
treatment system is only one of the removal mechanisms.
Chemical precipitation, coagulation, and sedimentation are believed to account
for the majority of phosphorus removal in an aquaculture treatment system.
Phosphorus, through chemical interaction becomes part of the bottom sediment.
In an aquaculture treatment system, there is an upper limit of phosphorus
removal which is established by the solubility of various phosphorus compounds.
Once the equilibrium is established, little additional removal of phosphorus can
be expected to occur unless the phosphorus-containing bottom sediment is
removed. The design life of an aquaculture treatment system relative to
phosphorus removal depends on influent phosphorus, the system volume and
bottom surface area. The literature indicates that aquaculture treatment
systems are similar in phosphorus removal efficiencies to conventional treatment
lagoons.
For nutrient-limited receiving water bodies, removal of nitrogen alone from
wastewaters before surface discharge may be effective in controlling
eutrophication. In these cases, removal of phosphorus from the wastewaters
may not be necessary. Otherwise, an aquaculture treatment system should be
designed to have ample capacity of phosphorus removal or operated in a fashion
so that removal of phosphorus-containing bottom sediments is practical at
predetermined intervals.
2.1.5 Removal of Heavy Metals
Heavy metals including radionuclei can be removed by several mechanisms
including plant uptake, animal metabolism, chemical precipitation, adsorption,
and ion exchange to settleable clay particles and organic compounds. It seems
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that the latter two mechanisms are most responsible for removal of heavy metals
in aquaculture systems. Obviously, sedimentation and filtration play a role in
removal of heavy metals after the metals are taken up by the plants and bound
by the clay and organic particles.
Colloidal clay particles and organic particles tend to be adsorbed to the plant
root systems. Harvesting the whole plant incidentally removes these colloidal
particles along with adsorbed heavy metals.
Certain aquatic plants may exhibit preferential metabolic uptake of specific
f n c 7 \
heavy metals. ' ' However, the extent of heavy metal removal by plant
uptake in aquaculture systems is not well-documented. Aquatic animals such as
oysters, clams or various filter-feeding fish may ingest certain heavy metals
(e.g. mercury, chromium, copper, cadmium, etc.) and show accumulations in
body tissues in concentrations several times that of the metal concentration in
the water column. When the equilibrium state is reached, heavy metals end up
partly in biological tissues, partly in bottom sludge, and partly in effluent.
2.1.6 Removal of Refractory Organics
Refractory organic compounds are not easily biodegraded in a conventional
biological treatment system, and such systems cannot efficiently remove
refractory organic compounds. Aquaculture treatment systems, due to
characteristically different biochemical and enzymatic conditions, and long
hydraulic detention times, may be effective in removal of refractory organic
compounds. Plant uptake, microbial enzymatic reactions, absorption, and
adsorption are believed to be major mechanisms responsible for removal of
refractory organic compounds from the water column. Among these mechanisms,
microbial metabolism and enzymatic breakdown are considered to be the
predominant removal mechanisms. These mechanisms also occur in conventional
treatment lagoons but reactions occur at slower rates than in an aquaculture
treatment system.
2.1.7 Removal of Bacteria and Viruses
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Aquaculture treatment systems have been shown to provide removal of enteric
bacteria and pathogenic viruses. Similar to conventional treatment lagoons, the
bacterial and viral removals in an aquaculture treatment system are attributable
to natural die-off accompanying long residence times and the hostile
environmental (biological, physical, and chemical) conditions for such organisms
/2)
which prevail in an aquaculture treatment system.
The lack of warm-blooded host sites hinders the survival of these enteric
bacteria and pathogenic viruses. In addition, certain enzymatic intermediates
emitted by aquatic plants and microorganisms may create a biochemical
environment hostile to the survival of certain enteric bacteria and pathogenic
(2)
viruses. The extent of pathogen reduction by aquaculture treatment
systems, like conventional treatment lagoons, has not been shown to be
consistent.
2.1.8 Removal of Trace Contaminants by Aquaculture Treatment Systems
Most of the published research on aquaculture treatment systems reviewed
during this assessment emphasized removal of conventional pollutants (i.e. BOD,
TSS and nutrients like nitrogen and phosphorus). Relatively few studies have
evaluated aquaculture treatment systems for potential removal of trace
contaminants (e.g., refractory organics, heavy metals, pesticides, etc.) from
either municipal or industrial wastewaters.
(3)
McDonald used water hyacinth, alligator weed (Alternanthera philoxeroides),
reeds, and cattail for decontamination of radioactive water. Plants were grown
in a greenhouse at an air temperature range between 15°C and 31°C. Cesium
(Cs), strontium (Sr), and cobalt (Co) were used as indicators for uptake of
radioactive substances by aquatic plants. At the end of a four week study,
plants were recovered, digested, and analyzed for Cs, Sr, and Co. The
study results demonstrated the ability of actively growing aquatic plants to
decontaminate radioactive water. In general, bio-concentration by these aquatic
plants indicated reductions in volume of contamination by 98.8 percent for
reeds, water hyacinth, alligatorweed, and cattails for the indicator radioactive
elements tested.
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(4)
Wolverton and McKown .studied the removal of phenol by water hyacinth
using a bench-scale system and found that phenol concentrations were nearly
undetectable after 48 to 72 hours of detention in the treatment systems. Phenol
removal by bacteria on the plant roots was not confirmed and extracts from the
water hyacinth biomass did not contain detectable amounts of phenol. It was
postulated that phenol was, however, removed by the water hyacinth and
primarily metabolized to other compounds through enzymatic perioxidases and
phenol oxidases present in the water hyacinth.
A combination anaerobic filter /vascular aquatic plant system was developed and
tested by Wolverton and McDonald^ for removal of phenol and M-cresol from
contaminated river water. The common reed (Phragmites communis) and cattail
(Typha latifolia) were grown on top of two separate anaerobic filters. The reed
and the cattail systems were reported to remove 93 percent and 83 percent,
respectively, from 100 mg/1 phenol solutions. A plant-free control system
showed 60 percent removal at a detention time of 24 hours. The reed system
removed 69 percent of M-cresol from 100 mg/1 solutions and reed free control
system removed 58 percent after 24 hours of detention. It was observed that
the phenol and M-cresol were rapidly adsorbed on the filler media surfaces and
either assimilated and/or metabolized.
In Louisiana, Tridech and Englande studied the removal of both
conventional pollutants and U.S. EPA designated priority pollutants by various
aquatic plants. The study was conducted in three phases: field screening,
batch screening experiments, and continuous flow. Nine aquatic species
including duckweed, coontail, elodea, waterbonnet, alligatorweed , water
hyacinth, arrowhead, bulrush, and rush were tested.
In the field screening phase of the study, the concentration of trace
contaminants in plant tissue, and the accumulation factor (ratio of dry weight
pollutant concentration in plant tissue to poEutant concentration in the water or
sediment column) were analyzed. The results indicated that plant tissue
concentrations could range from hundreds to thousands of times that of the
corresponding water or sediment concentration. This bio-accumulating
capability indicates that removal of trace contaminants from wastewater by
aquaculture is possible.
2-9
-------
(fi 7^
In the batch-screening tests, ' secondary effluent from a trickling filter
treatment plant was used to acclimatize mature aquatic plants. Influent to the
test aquariums was spiked with 1 mg/1 of arsenic, 5 mg/1 of boron, 1 mg/1 of
cadmium, 1 mg/1 of mercury, 1 mg/1 of selenium, 1 mg/1 of phenol, and 0.03
mg/1 of polychlorinated biphenols (PCB-Arochlor 1254). All experiments were
conducted in a greenhouse under temperature conditions of 21 to 23°C. Each
batch run was terminated at day 28. Results, given in Table 2.1 demonstrated
that, in general, aquatic plant systems were effective in removing cadmium,
mercury, phenol, and PCB's; exhibited some removal of boron; but showed little
removal of arsenic and selenium, except bulrush and rush. The systems were
effective in converting ammonia and removing total nitrogen, but less effective
in removal of phosphate. Phosphate removal seemed to be limited by availability
of nitrogen. Similar to other aquatic processing units, the experiments showed
effective removal of BOD_ and TOC, especially for rooted plants such as
3
bulrush, rush, and arrowhead, and submerged alligatorweed.
With the aid of kinetic models, Englande and Tridech were able to determine a
series of kinetic coefficients for various aquatic plants. These kinetic
coefficients are most important in designing aquatic processing units for removal
of trace contaminants. The same technical approach can be applied to removal
of conventional pollutants (BOD,., TOC, TSS, ammonia nitrogen, total nitrogen,
0
etc.) provided that the test environmental conditions are conducive for plant
growth and do not impose phytotoxicity problems. Since the kinetic studies
were conducted in a controlled temperature environment, and since biological
and chemical reactions are influenced by ambient air and water temperatures,
the effects of temperature on these kinetic coefficients remains to be explored
and determined prior to actual design applications. In addition, the threshold
values of various trace contaminants, beyond which significant phytotoxicity
occurs, needs to be determined for the various candidate aquatic plant species
for wastewater aquaculture. Nonetheless, this approach to determining rate
coefficients represents a significant advancement in understanding the removal
mechanisms involved in an aquatic process unit, which hopefully will lead to
better selection and design of future aquaculture treatment facilities.
/C r»N
Englande and Tridech ' also found that, almost universally, aquatic plants
exhibit initial rapid uptake of trace contaminants, like cadmium, which gradually
2-10
-------
Table 2.J,
RELATIVE UPTAKE EFFICIENCY OF WASTE CONTAMINANTS
BY AQUATIC PLANTS IN BATCH STUDY: 28-DAY DETENTION TIME
(6,7)
Plant
Bulrush
Rush
Arrowhead
Water Hyacinth
Duckweed
Waterbonnet
Coontail
Elodea
Alligator Weed
Algae
Control
(no plants)
Pollutant (% removal)
As B Cd Ha Se Phenol PCB Tot-N PO^, BODC TOC
82.14
54.22
10.53
12.50
10.26
0.62
15.82
20.75
11.80
4.35
14.62
12.64
16.47
12.46
16.95
10.67
17.63
17.52
14.62
10.91
1.49
98.85
91.44
78.41
68.60
68.00
24.85
91.11
85.71
76.30
46.17
22.75
92.75
79.13
74.17
70.16
68.86
47.42
70.01
79.19
75.18
62.20
60.39
94.89
61.80
29.77
8.19
10.98
6.11
28.89
18.28
10.52
0.00
0,00
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
57.14
100
100
100
87.50
66.67
99.62
99.97
62.73
41.70
50.55
58.53
92.28
94.23
96.50
72.23
59.99
89.55
65.41
7.51
13.30
17.67
20.59
-4.64
8.19
38.06
-0.71
-0.91
87.70
92,66
85.28
21.76
14.44
-5.00
23.33
49.28
82.57
30.36
-7.55
59.52
70.15
61.15
18.04
18.8-
47.6
r
1.55 '
18.94
54.05
57.60
6.15
1.75 ;
-------
approaches an equilibrium level after approximately 10 to 30 days. The rate of
uptake varies with plant species and contaminant concentration. This finding
indicates the necessity of harvesting mature plants from the system in order to
remove the trace contaminants continuously. Two mathematical models were
proposed by Englande and Tridech to describe absorption or tissue uptake
kinetics for various vascular aquatic plants.
Based on the results of the batch screening study, a continuous flow study
with and without effluent recirculation was conducted for water hyacinths and
bulrushes. Selection of water hyacinth and bulrushes for continuous flow
studies was also based on practical considerations such as productivity of the
plants, ease of harvesting, and high removal capacity for most trace
contaminants. The experimental results for continuous flow without
/ /> rr \
recirculation and with 1:1 recirculation are summarized in Table 2.2. ' It
can be seen that overall removal of all pollutants was better with aquatic plants
than in the control system without plants. Removal of fecal coliforms by the
control system and planted systems is believed to be primarily due to natural
die-off resulting from the hostile environment in the bench scale treatment
systems. Improved removal by effluent recirculation may be the result of
increased probability of contact between the liquid and plants, increased
renewal rate of reactive interfaces, and stabilization of overall treatment
process, which are the basic governing design principles for the design of
conventional trickling filters and biological towers with plastic media for
(fi 7^
bacterial growth (a fixed film treatment process). '
2.2 Existing Wastewater Aquaculture Facilities
Although interest in wastewater aquaculture technology has increased, in part
due to construction grant funding incentives through EPA's
Innovative/Alternative (I/A) Technology Program, application of wastewater
aquaculture technology remains primarily an academic interest. Full-scale,
permanent application of wastewater aquaculture technology is still rather rare.
This Section summarizes the treatment objective, size, and level of performance
of reported, existing aquaculture treatment systems.
2.2.1 Existing Aquaculture Treatment Systems Using Aquatic Plants
2-12
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Table 2.2
REMOVAL OF TRACE AND CONVENTIONAL POLLUTANTS
(6,7)
BY WATER HYACINTH AND BULRUSH
(0
1
M
Ul
Det .Time
System BOD TOC As B Cd Hg Se Phenol PCB TN PO, TSS VSS F. Coli Eff. pH. (days)
Water Hyacinth
without Recirculation
Water Hyacinth
with 1:1
Recirculation
Bulrush without
Recirculation
Bulrush with
1:1 Recirculation
Control (no plants)
without Recirculation
Control (no plants)
with Itl
Recirculation
* Increased
95 80 41 36 85 92 60 97 98 85 65 99 99 99.5
95 70 52 11 61 96 51 89 100 84 19 98 97 99.9
76 66 56 36 91 93 85 96 95 75 52 94 91 95.3
95 68 63 37 90 98 91 86 100 88 17 99 98 99.9
70 27 7 0 81 82 45 72 26 73 22 81 73 94.5
81 48 23 * 39 93 21 77 100 76 * 89 86 98.3
7.0-7.6
6.9-7.7
7.2-7.7
7.2-7.8
8. 3-9.. 3
7.9-8.3
15
7 .5
15
7.5
15
7 .5
-------
Aquaculture treatment systems using aquatic plants rather than fish or aquatic
invertebrates seem to be predominant in the application of wastewater
aquaculture technology. Many aquatic plant species including water hyacinths,
reeds, bulrushes, cattails, duckweed, alligatorweed, primrose, kelps and others
are potential candidates for aquaculture treatment systems.
Existing operative aquaculture treatment systems which use aquatic plants are
listed in Table 2.3. As indicated, water hyacinth has been the most commonly
used plant for wastewater aquaculture facilities. Reeds/bulrushes rank second,
Duckweeds are the third most popular aquatic plant species in aquaculture
treatment systems. Existing aquaculture treatment system using aquatic plants
tend to be relatively small-flow facilities since:
Most systems are experimental or pilot plant size and thus tend to be
small-flow facilities; and
Land requirements for aquaculture treatment systems tend to favor its
application in rural areas where large flows are not generally found.
Most of the existing documented aquaculture treatment facilities are of a various
research nature and have been sponsored by U.S. federal governmental
agencies and research institutions including the National Aeronautic and Space
Administration (NASA), the U.S. Environmental Protection Agency (EPA), the
National Science Foundation, Woods Hole Oceanographic Institution, Tennessee
Valley Authority, Tulane University, University of California at Davis,
Humboldt State University, Florida State University, Michigan State University,
and Walt Disney World. Few projects have been privately funded. A great
majority of the systems treat domestic or municipal wastewater with emphasis on
renovation of secondary effluent or lagoon effluent. The lack of research funds
or the termination of a research project was found to be the primary cause for
many systems becoming non-operative. Only a few systems have become
non-operative because of system problems such as plant die-offs or mosquito
infestations. The identifiable non-operative plant-based aquaculture treatment
systems are listed in Table 2.4. In general, technical reports on existing
systems are limited to those of an experimental nature.
2.2.2 Water Hyacinth Aquaculture Treatment Systems
2-14
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Table 2.3
EXISTING PLANT WASTEWATER AQUATIC
PROCESSING UNITS (APU)
Location
Species Used
Treatment
Objective
Flow (MGD)
Description
N.S.T.L.,
Bay St. Louis, MS
Shreveport, LA
Paragould, AS
N. Biloxi, MS
Gregory, TX
Austin, TX
Rio Hondo, TX
hyacinth,
duckweed
hyacinth
duckweed
duckweed
hyacinth
hyacinth
hyacinth
photographic
wastewater
raw
wastewater
screened raw
wastewater
primary
effluent
aerated
lagoon
effluent
secondary
effluents S
stormwater
waste activated
sludge
stabilization
pond effluent
0.024
N/A
0.014
2.2
0.013
0.14
1.6
0.12
hyacinth lagoon
(zig zag)
hyacinth &
duckweed lagoon
hyacinth lagoon
(spray irrigated
when cold)
lagoon
0.08 Ha aerated
lagoon duckweed;
duckweed pond
ditch with hyacinth;
lake with hyacinth
3 sludge ponds in
series? hyacinth
pond
stabilization pond?
3 hyacinth ponds in
series
Imhoff tank;
stabilization pond;
2-15
-------
1
Location Species Used
Edcouch, TX
Coral Springs, FL
Walt Disney World,
FL
Plant City, FL
Chapel Hill Independent
School District, TX
Hanover, NH
N.S.T.L.
Bay St. Louis, MS
1 Lake Helen, FL
hyacinth
hyacinth
hyacinth
hyacinth
hyacinth
cattails
vegetables
anaerobic
filter/reed
hyacinth
Treatment
Obiective Flow (MGD)
pond effluent 0.14
secondary
effluent 0.1
primary
effluent 0.063
secondary effluent 4.0
raw wastewater 0.02
primary
effluent 0.003
septic tank
effluent N/A
primary 0.007
Description
ponds
hyacinth ponds in
in series
3 hyacinth lagoons
in series
hyacinth pond
hyacinth pond
nutrient film
technique
anaerobic filter/
reed system
4 lagoons in series
methane generation
2-16
-------
Table 2.4
ABANDONED PLANT APU'S
Plant (a)
Location Used
San Marcos, TX
Rio, TX
(San Juan)
Rio, TX
(Alamo)
San Benlto, TX
Gainesville, FL
U. of n.
Lakeland, FL
Caserne, FL
Lucedale, MS
Orange Grove, MS
Baytown. TX
(Exxon)
St. Helena, CA
Forestville, CA
Occidental, CA
Plney Woods Baptist
Encampment, TX
Texarkana, TX
Lewlsvllle, AK
Hyacinth
Hyacinth
Hyacinth
Hyacinth
Hyacinth
Hyacinth
Hyacinth
Hyacinth
Hyacinth
Hyacinth
Hyacinth
Hyacinth
Hyacinth
Hyacinth
Hyacinth
Hyacinth
Treatment Objective
Aerated wastewater
Stabilization pond
effluent
Stabilization pond
effluent
Stabilization pond
effluent
Secondary
effluent
Secondary
effluent
Secondary
effluent
Raw wastewater
Aerated lagoon
effluent
Stabilization
pond effluent
H/A
H/A
N/A
N/A
N/A
H/A
Flow
-------
Water hyacinths (Eichhornia crassipes) are .large floating aquatic plants that
were introduced into the southern United States from tropical regions.
Research has indicated that water hyacinth production is on the order of 1,000
to 10,000 wet-pounds/day-acre (1,120 to 11,200 kg/ha-day), ranking it as one
of the most productive plants on earth. Water hyacinth plants have been found
(8 9 10)
to grow at a rate of 10 percent of their surface area per day ' ' and
thrive in raw or partially treated sewage. In fact, hyacinth growth in treated
sewage is reported to be double the growth rate in natural waters. Water
hyacinths are relatively resistant to insects and disease, are unaffected by pH
variations from 4 to 8, but are sensitive to high salinity and above-water plant
tissues die back rapidly as temperatures approach freezing. Due to
temperature effects, water hyacinth has a very limited geographic range without
auxiliary heating or cover of hyacinth ponds. The water hyacinth contains
between 0.7 percent and 3.7 percent nitrogen and between 0.1 percent and 0.9
percent phosphorus on a dry weight basis. This is equivalent to a nitrogen
removal potential of approximately 770 kg/ha-yr and a phosphorus removal
(12)
potential of approximately 180 kg/ha-yr based on 95 percent water content .
The high growth rate, resistance to insects, disease and presence of an
extensive root system where microorganisms can attach, are favorable
characteristics' of the water hyacinth and have led to its popularity in
(13)
wastewater aquaculture technology .
Basically, wastewater aquaculture treatment by water hyacinth is currently
accomplished by passing raw or pre-treated wastewater through a basin, or
series of basins, covered with water hyacinths. Through the complex
mechanisms discussed previously, the plants remove BOD, suspended solids,
nutrients, metals, and possibly other contaminants. Harvested hyacinths from
these systems have potential use as fertilizer/soil conditioners, animal feeds,
and as a source of methane through anaerobic digestion, after appropriate
handling and processing steps.
Most of the existing hyacinth treatment systems are in the development stage.
The ability of water hyacinths to remove BOD, SS, nutrients, metals, and
certain organic compounds from wastewaters has been documented in laboratory
scale studies. A number of full scale experimental and demonstration systems
2-18
-------
have also been implemented. However, most of the work with water hyacinth
treatment systems has sought to monitor and document overall treatment effects
rather than to describe and quantify removal mechanisms and specific removal
rates at various stage of growth, under various environmental stresses. The
continued study of removal mechanisms and rates is necessary if optimization
system design and operation criteria is ever to be achieved.
The ability of water hyacinths to remove BOD and suspended solids enables
hyacinth-based technology to be applied to treatment of raw municipal and
domestic wastewaters, primary effluents and stabilization pond effluents. The
ability to remove heavy metals and organic compounds implies that water
hyacinth systems may also be used in treating certain industrial wastewaters.
Certain types of industrial wasteflows have been experimented with in
hyacinth-based systems. The results of these experiments are discussed in
Chapter 3.
Most frequently, water hyacinth systems have been used as an advanced
treatment process to remove nutrients from conventional secondary treatment
plant effluents or to retard algal growth in conventional lagoon treatment
systems. Reducing algal growth in conventional treatment lagoons by planting
(14)
and growing water hyacinths has been documented. While these studies
used effluent suspended solids as an indicator of algal growth, it is believed
that additional evidence supporting the supression of algal growth by water
hyacinth coverage could be provided by measuring chlorophyl-a concentration.
Climate is a major constraint in implementing a water hyacinth treatment system.
Active growth of water hyacinth begins when the water temperature rises above
10°C (50°F) and flourishes when the water temperature is approximately 21°C
(13)
(70°F). This water temperature range can only be maintained
cost-effectively in regions of the United States where above freezing
temperatures occur on a year-round basis. Water hyacinths die rapidly when
the water temperature approaches the freezing point. Greenhouse construction
would be necessary in those states where winter freezes occur if water hyacinth
systems were to be used on a year-round basis.
2-19
-------
Water hyacinth treatment systems characteristically require large acreage. It
has been estimated that 2 to 15 acres of land is required to treat a 1 MGD flow.
Therefore, water hyacinth treatment systems may not be practical in areas
where land is not economically available.
As indicated previously, continuous or periodic harvesting of water hyacinths,
especially the selective harvest of those plants showing symptoms of aging, is
desirable to maintain treatment efficiency. Due to the large size of the- plants,
harvest is more readily accomplished for hyacinth than for other aquatic species
such as duckweed or algae. Several harvesting techniques have been tried.
These include on-shore drag lines fitted with clam-shell buckets, retrievable
nets, and specially designed mechanical harvesters.
(14)
The water hyacinth is normally 92 to 95 percent water. If the harvested
plants are to be used as fertilizers/soil conditioners or in animal feeds,
extensive dewatering/drying is necessary. In order to release inter-cellular
water, the water hyacinths need to be chopped or shredded. Further
dewatering can be achieved through mechanical pressing. However, the most
cost-effective method of drying hyacinths is through solar energy on drying
beds. Greenhouse construction may be necessary in some parts of the country
to facilitate this drying process. Composting dewatered water hyacinths is a
potential means of stabilizing water hyacinths for later use as a soil conditioner.
Use of water hyacinths for fertilizers/soil conditioners or animal feeds may be
limited when heavy metal and other toxic substance concentrations are
accumulated in the water hyacinth tissue. -Anaerobic digestion of water
hyacinths to generate methane gas would be a possible use for these plants.
However, maintenance of proper conditions in the digesters may not always be
possible in many parts of the country without auxiliary heating of the digesters
in cold weather periods. In addition, anaerobic sludge from the digesters
needs to be disposed of in an environmentally sound manner.
2.2.3 Duckweed Aquaculture Treatment Systems
Duckweeds, (Lemnaceae), are among the smallest floating plants known. The
Family Lemnaceae consists of the genera; Wolffiella, Wolffia, Spirodela, and
Lemna. In most instances, mixed cultures of duckweed species are found.
2-20
-------
It has been estimated that the productivity of mixed duckweeds growing in
wastewater lagoons is approximately 37 dry kkg per hectare per year (16 dry
tons/acre-yr). The water content of fresh duckweed is approximate^ 95
percent. Therefore, this productivity is equivalent to 350 wet kkg/ha-year (or
310 wet tons/acre-yr). Duckweed contains from 1.2 percent to 7.2 percent
nitrogen and from 0.2 to 2.8 percent phosphorus on dry weight basis. This
equates to a nitrogen removal potential of approximately 550 to 750 kg/ha-year
(490 to 670 pounds/acre-yr) and a phosphorus removal potential of 140 to 260
kg/ha-yr (or 125 to 230 pounds/acre-yr). This higher nitrogen content
found in duckweeds gives it a higher feed value compared to most aquatic
plants.
Duckweed species, in general, are more tolerant of cold weather than water
hyacinths. It has been reported that common duckweed vegetates at
temperatures as low as l°Cr ' ' and will survive light freezes. Duckweed
growth has been found to continue at a slower rate during the winter months,
and thus it may be applied to aquaculture treatment systems over a much wider
geographical area than water hyacinths. However, in areas where severe and
extended winter periods occur, greenhouse construction would be necessary to
assure process reliability.
The rapid growth, ease in harvest by screening or straining, longer growing
season and relatively favorable feed value of duckweed render it a prominent
candidate for wastewater aquaculture treatment systems.
Current wastewater aquaculture treatment systems using duckweed are similar to
water hyacinth treatment systems. Raw wastewater or pretreated wastewater is
introduced to a basin or multiple basins in series which are covered with
duckweed. Through previously discussed mechanisms, duckweeds facilitate the
removal of BOD, suspended solids, organic compounds and heavy metals from
the water column. Because the root zone is much shallower than that of the
water hyacinth, removal of suspended BOD and other suspended solids via root
zone filtration by duckweed is much less than by water hyacinth.
Most of the existing duckweed treatment systems are in the development or
experimental stage. It has been demonstrated that duckweed can effectively
2-21
-------
remove BOD, SS, nutrients, and trace contaminants from wastewaters in
laboratory and pilot scale studies. At the time of this study there were two
demonstration systems in operation. One system at Biloxi, Mississippi polished
the effluent from an aerated lagoon treating raw sewage. The other treated
dairy farm wastes in a study at Louisiana State University, Baton Rouge,
Louisiana. The level of performance of the Biloxi, Mississippi system plus the
results of a three-month winter test conducted at National Space Technology
Laboratories (NSTL), Bay St. Louis, Mississippi, are given in Table 2.5.
( 1 fi ^
A small laboratory scale study conducted by the University of Florida to
determine the nutrient removal potential of duckweed, demonstrated that nitrate
nitrogen removal efficiencies were 0, 10, 20, 28 and 29 percent for detention
times of 2, 4, 6, 8 and 10 days, respectively. The nitrate nitrogen removal
essentially reached equilibrium level at a detention time of 8 to 10 days.
Removal efficiencies of phosphorus attributable to duckweed uptake were
approximately 6, 9, 23, 34 and 48 percent for detention times of 2, 4, 6, 8 and
/1 /> \
10 days, respectively. Apparently, the equilibrium phosphorus removal
rate was not attained in this experiment, because the detention time was not
long enough and mechanisms discussed previously would affect this equilibrium
removal rate. This laboratory scale test also demonstrated the rapid growth
rate of duckweed. Lemna was found to double in frond number, and thus area
" / n Ł» \
of coverage, every 4 days under favorable environmental conditions. Thus,
if an acre (0.4 ha) of effluent was one-fourth covered by Lemna at Day 0, at
Day 8, it would be completely covered. Other interesting preliminary findings
t 1 C \
of this study were:
Wolffia columbiarta, while having a high digestability (or dietary)
value, was found to be difficult to harvest.
Salyinia rotundifolia was found to contribute large amounts of detrital
material to the benthos and was found to have a very low
digestability (or dietary) value.
Similar to water hyacinths, duckweed treatment systems require relatively large
land areas. Duckweed treatment systems probably can be cost-effective in
areas where land is economically available. Continuous or periodic harvest of
duckweed, especially mature individuals is the key to maintaining maximum
system productivity and treatment performance. Harvesting duckweed is
2-22
-------
Table 2.5
PERFORMANCE OF DUCKWEED AQUATIC TREATMENT SYSTEMS
Location
Type of
Wastewater
Applied
Influent (mg/1)
BOD TSS
Effluent (mg/1)
BOD TSS
Percent Removal
BOD TSS
to
U)
North Biloxi, MI
(Wolverton, 1979)
National Space
Technology Lab
Bay St. Louis, MS*
(Wolverton, 1979)
Effluent from
Aerated Lagoon
Domestic
Sewage
Aerated
Lagoon
Effluent
16-37(35)
61-397(155)
8-28(15)
8-22(14)
15-69(48) 80-98(88)
69-90(82)
88-132(111)
2-7(3.7)
8-14(10)
92-98(96) 89-93(91)
* 3-Month experiment in winter
-------
relatively more difficult than harvesting water hyacinths due to the smaller size
of duckweed. Skimmers, strainers, screen buckets, screens, and similar
devices (manual or automated systems) have been used for harvesting
duckweed.
The handling and processing of harvested duckweed may include dewatering,
drying, composting, anaerobic digestion and/or other processing steps as
necessary. Potential end uses of harvested duckweed include animal feed
supplements, and soil conditioners.
2.2.4 Reed/Bulrush Aquaculture Treatment Systems
Reeds or bulrushes are emergent rooted aquatic plants. There are several
experimental systems using reeds and/or bulrushes. Among the varieties of
reeds and bulrush, Phragmites communis (a reed), Scirpus lacustris (a
bulrush), and Scirpus validus (a soft stem bulrush) have been tested
(2 18 19)
successfully for vcastewater treatment. ' ' In the aquaculture treatment
field, aquaculture treatment systems using emergent aquatic plants including
reeds, bulrushes, cattails, etc. are considered forms of artificial wetland
treatment systems, and are discussed further in Section 2.3.6.
2.2.5 Existing Combined Aquaculture Treatment Systems
A combined aquaculture treatment system, or polyculture treatment system, is
generally defined as one in which wastewater treatment is accomplished by
several different trophic levels of cultured aquatic organisms. In typical
polyculture treatment systems, carbonaceous compounds are broken down
biologically by microorganisms and nutrients are first converted to single-cell
organisms or lower forms of plants that serve as food for organisms of higher
trophic levels in the same aquatic processing unit (APU) or in subsequent
APU's.(20)
There are fewer existing combined aquaculture treatment systems than systems
using aquatic plants only. Those facilities using combined APU's are most often
associated with other plant APU's or wetlands APUs due to the fact that in
2-24
-------
general, a polishing APU using plants is necessary to further renovate effluent
in order to remove animal wastes. A number of the combined processes that
have been reported are illustrated in Figure 2.1. In addition, available
information regarding the combined aquaculture treatment or polyculture concept
results from research and demonstration projects that have been terminated.
Table 2.6 lists some of the published polyculture research projects.
When floating aquatic plants (e.g. duckweed, water hyacinth, etc.) are used in
an aquaculture treatment system, it is possible to grow selected fish or aquatic
invertebrates in the same pond. In general, duckweed or water hyacinth ponds
are shallow (liquid depth of 3 to 4 feet) and are subjected to winter freezing.
This may adversely affect the growth of aquatic animals in the system and thus
result in poor system performance in winter. For a combined system using
bulrushes and reeds grown hydroponically, the animal APU requires a separate
pond. Algae ponds in a combined aquaculture treatment system, in general,
should precede and be separated from any aquatic animal ponds to eliminate low
dissolved oxygen problems in the aquatic animal ponds. Combined aquaculture
treatment systems are not usually used to treat raw sewage directly. They are
used most often to renovate secondarily treated effluent. In general, combined
aquaculture treatment systems are not as easily controlled as aquaculture
treatment systems using aquatic plants only. .
The Quail Creek Wastewater Treatment System, Oklahoma City, Oklahoma used
six ponds in series, the first two of which were artificially aerated. Tilapia,
fathead minnows, and channel catfish were grown in the third pond, channel
catfish in fourth pond, and golden shiners and minows in the fifth and sixth
(21) (24)
ponds. Another system at the Village of Dorchester, Wisconsin used an
aerated sewage treatment lagoon for rearing muskellunge fingerlings.
Conventional lagoon treatment and aquaculture treatment were accomplished in
the same lagoon. In addition, a 6-pond system utilizing silver carp
(Hypothalroichthyes molitrix) and big head carp (Aristichthyes robilis) for the
-————-—_————. __
treatment of primary effluent was used in experiments by Henderson
(22)
Researchers at Michigan State University used four ponds in series to test
the performance of the combined aquaculture treatment concept on primary and
secondary effluents. The first pond was intended primarily as an algae pond
2-25
-------
Figure 2.1
POSSIBLE LIQUID PROCESS TRAINS FOR
COMBINED AQUACULTURE TREATMENT SYSTEMS
to
APU
(Aquatic Plants)
APU
(Aquatic Animals)
Post-Treatment
Process
APU
(Aquatic Plants and Animals Combined)
Post-Treatment
Processes
APU
(Aquatic Plants)
APU
(Aquatic Animals)
APU
(Aquatic Plants)
Post-Treatment
Processes
APU
(Aquatic Plants and Animals Combined)
APJJ
(Aquatic Plants)
Post-Treatment
Process
-------
Table 2.6
polyculture (Combined) APU Research Projects
Plant(s) ,
Animal (e)
Location Weed
Quail Creek, OK
Enid, OK
Oak Ridge Lab, TO
Austin, TX
Hoods Hole, MA
Harbour Branch, PL
Eolano Beach, CA
Hercules, CA
Michigan State
Uhivmrsity, MI
Ben ton Services
center, AS
Catfish, tllapia
golden shiner
minnows
fish, mussels
water primrose
Tilapia
shrimp, snails
fathead minnows
goldfish,
carp tilapia
Algae
shellfish
Algae, carp,
shrimp
Hyacinth
duckweed
invertebrates
Hyacinth
invertebrates
Algae, Zlodea
Largemouth
bass
Silver, Bighead
Carp
Treatment Objective
2' effluent
Refinery wastewater
toxicity
2* effluent
Filtered
secondary
effluent
2" effluent
2* effluent
2' effluent
1° effluent
1*.2» effluent
2* effluent
Flow
(MGD)
1,0
0.014
0.023
O.O3
O.OO8
0.002
0.001
0.35
0.5 MGD
0.4 MGD
Description
6 lagoons in series)
fish in last 4
6 pools in series)
algae first 3 and
plants in last 3
2 oxidation ponds in
series containing fish
Hyacinths
duckweed, snails, scud
1st unit) loop lank ton in
2nd unit, shrimp and
fish in final 2 unite
Cultured alcjaei mixed
with seawater/ fed to
shellfish (mariculture)
Cultured algae fed
to fish and shrimp
Solar aquacell process
Solar aquacell process
4 ponds in series;
algae in 1st, elodea
in last 3, with bass
in final
6 lagoons in series;
1st, 2nd with algae
& plankton culture,
final 4 with fUh.
Reason for Abandonment
Research terminated
Research terminated
Research terminated
Research terminated
Research terminated
Research terminated
Research terminated
Operational problems
Being phased out
Experimental, pilot
•cale .
to
I
to
-J
-------
supporting periphytic algae species. After a brief bloom of planktonic algae,
the other three ponds were dominated by the macrophyte Elodea canadensis.
Largemouth bass were grown in the last pond. It was noted that the growth of
largemouth bass was very rapid from average body length of 4.4 cm (1.7
inches) to 24.9 cm (9.8 inches) in approximately 12 months.
(27)
Binges studied, on a pilot scale basis, a five-step biological treatment
system consisting of a filter and a four-cell culture unit. The system was
designed to treat the effluent from a stabilization lagoon after filtration. The
first cell, approximately one-half of the culture unit, contained water
hyacinths, duckweeds, snails, scuds, and various insects. The second cell was
designed to culture zooplankton and duckweed, with the duckweed intended to
suppress algal growth. Shrimp and fish were grown in the third and fourth
cells, respectively.
The treatment performances of the aforementioned systems, summarized in Table
2.7, indicate removals of BOD, TSS, and total nitrogen greater than 67
percent, 55 percent, and 60 percent depending on influent quality. Removal of
total phosphorus greater than 74 percent is possible in the earlier stage of the
(21)
systems. However, long-term removal of total phosphorus is rather low,
approximately 17 percent, as demonstrated by the Benton, Arkansas project
9fi \
after several years of experiments. ' This may be attributable to the
saturation of phosphorus in the pond sediments and loading or breakthrough of
soluble phosphorus.
2.2.6 Natural Wetlands Aquaculture Treatment Systems
Natural wetlands, both marine and freshwater, have inadvertently served as
natural waste treatment systems for centuries. U.S. EPA Regions IV and V are
currently inventorying the use of natural wetlands areas for waste water disposal
in those regions, in efforts to quantify and qualify environmental impacts. The
managed use of wetlands for wastewater treatment is a relatively recent
(29)
development dating back to the early 1960's Table 2.8 lists a number of
published facilities where wetlands are either utilized as disposal sites (in many
cases having discharged for several decades) or managed as tertiary treatment
sites. The list is by no means complete, as the EPA's region V alone has
2-28
-------
Table 2.7
LEVEL OF PERFORMANCE OF
COMBINED AQUACULTURE TREATMENT SYSTEMS
!
Prelect
Juail Creek,
Oklahoma City,
OK
i/illage of Dorchester,
Wausan, WI
I Michigan State University
East Langing, MI
5-Step Polyculture
System, Williamson
Creek, Austin, TX
Benton Service Center,
AS
1
Averaqe Removal Percent
Fee. Period of
Influent BOD TSS Total N Total P Coli Experiment
Secondary
Effluent 75 83 61 74 98.6 4 TOO.
Raw
Sewage 97.5 96.4 — ~ — 2 yr.
Primary or
Secondary
Effluent — « 98 98 — existing
Filtered
Secondary
Effluent 77 80 81 — 99
Primary &7 55 60 17 — 2 yr.
Effluent
References C20-26)
2-29
-------
Table 2.8
EXISTING NATURAL WETLANDS TREATMENT SITES
1
1
1
1
1
1
1
1
1
J
Location
Mt. View Sanitary
District, CA
Beaver Bay,
MN
Wildwood,
FL
Walt Disney
World, FL
Drummond,
WI
Houghton Lake,
MI
Vermontville,
MI
Concord
MS
Brillion Marsh,
ws
Gainesville,
FL
Objective Size
treatment of
2° effluent .7 MGD
tertiary treatment
of 2° effluent .04 MGD
disposal of
2° effluent N/A
disposal of
2° effluent 2.0 MGD
pipeline irriga-
tion of 2°
effluent .01 MGD
tertiary treatment
of 2° effl-uent
.01 MGD
tertiary treatment
of 2° effluent
.5 MGD
discharge of
2° effluent .61 MGD
tertiary treatment
of 2° effluent .02 MGD
tertiary treatment
of 2° effluent .0015 MGD
Type of
Wetlands
volunteer
marsh-forest
peatland
natural cyprus
dome wetlands
pine and
cypress wetlands
bog, adjacent to
hardwoods &
sphagnum wetlands
marsh peatland
wetlands
volunteer cattail
marsh
deep marsh-Nat ' 1
Wildlife Refuge
natural freshwater
marsh
cypress dome
swamps
Remarks
existing
N/A
N/A
existing
N/A
existing
existing
18 Mos.
Study
existing
2-30
-------
identified 96 sites using wetlands areas for disposal. There are undoubtedly
numerous unpublished natural wetlands disposal sites throughout the United
States.
In recent years, marshes, swamps, bogs, peatlands and other wetlands have
been successfully utilized as managed natural "nutrient sinks" for polishing
partially treated effluents. Natural wetlands areas receiving managed
discharges of secondary effluent for tertiary treatment purposes are numerous.
Houghton Lake, Michigan is one such facility where research beginning in 1972,
led to the 1978 construction of a gated-pipe irrigation system to disperse
secondary municipal effluent over 600 acres of natural wetlands for the purpose
(31) (32)
of tertiary treatment. Williams and Sutherland identify five other
wetlands areas in Michigan alone where municipal wastewater/wetlands effects
are being investigated. These include Kinross, Lake Odessa, Vermontville, Paw
Paw and Leoni Township.
Cypress dome wetlands have demonstrated the potential for providing tertiary
treatment of secondary effluent while remaining environmentally sound.
Cypress dome wetlands are characteristically saucer-shaped swamps containing
cypress trees, the tallest of which are located in the center of the dome. The
bottom of the ponds are coated with organic sediments and clay, which promote
(33)
slow filtering of the wastewaters through soil. Trees rooted in the soil
with attached bacteria, and pond surface duckweeds facilitate treatment of the
wastewater as it passes through the system to underlying groundwaters.
Secondary effluent from a mobile home park located near Gainesville, Florida
was purposely applied to a cypress dome wetland location for research
purposes. Ninety-eight percent of the total nitrogen and 97 percent of the
(34)
total phosphorus was removed before entering the underlying groundwater.
Other monitored parameters in the groundwater of two test domes and control
units were below Federal Drinking Water Standards.
The discharge of wastewater effluents to cypress wetlands has occurred in
other locations in Florida as well. A cypress strand wetlands in Jasper, Florida
has also received discharges of secondary effluent for several years, and is
(35)
being evaluated for tertiary treatment efficiency.
2-31
-------
Phosphorus removal mechanisms in wetlands aquaculture treatment systems are
significantly affected by the type of soil present in the wetlands and the
sorption, ion exchange and precipitation reactions taking place between the soil
and wastewater. The most significant nitrogen removal mechanism appears
/ o c \
to be bacteria] nitrification/ denitrification processes.
The removal of nitrogen and phosphorus is also affected by vegetative uptake,
and the frequency of harvesting. Harvesting is not commonly practiced for
natural wetland systems.
BOD removal information and loading rates have been summarized by Stowell, et
( 33)
al for peatland and marsh systems. It was observed that effluent BOD was
relatively constant, better than conventional tertiary treatment systems, and
relatively independent of influent BOD for natural wetland systems. In
addition, BOD removal rates (BOD removed per unit area and unit time) were
reported to be a linear function of BOD loading rates as long as detention times
generally greater than 15 days were provided, and BOD loading rates were less
/*> C \
than 80 kg/ha-day (approximately 70 pounds/ day).
Secondary effluents may provide a unique opportunity to recover damaged or
stressed wetlands while properly disposing of the treated effluents at the same
time. Wildlife habitat enhancement of this kind has been successfully
(37)
demonstrated in Mountain View Sanitary District, California. The 23-acre
reclaimed wetlands area studied included open water areas, open water areas
with artificial substrates for aquatic invertebrate, populations (called ecofloats);
mud flats and cultivated areas of floating and emergent vegetation, levees and
adjacent wet lands with terrestrial grasses, shrubs and trees. The plant
species occurring indigenously in the wetlands numbered 72, and 90 species of
(37)
birds were identified living in or visiting the wastewater created wetlands.
In addition to the resultant flourishing wildlife habitat, wastewater effluent
quality improves as it passes through the wetlands environment. Data indicate
fluctuating levels of nutrients, BOD and suspended solids, all which are
affected and changed by the life cycles taking place in the ecosystem.
(37)
Demgen stresses that BOD and suspended solids contained in the wetlands
effluent is in a highly useable form; comprised mainly of algae cells and other
2-32
-------
organisms that are primary food sources in the aquatic environment. The
recycling effect afforded by the wetlands environment alters the unuseable
nutrients, BOD and suspended solids of human waste origin to plant biomass
and other natural forms.
Wetland treatment .systems are relatively land intensive (perhaps not as land
intensive as slow-rate irrigation land treatment) requiring land in the order of
8 to 10 acres per million gallons per day. ' Therefore, wetland systems may
prove impractical for large treatment facilities due to the extensive land
requirements.
2.2.7 Artificial Wetlands Aquaculture Treatment Systems
The construction of artificial wetlands systems has been proposed as an
alternative to conventional treatment processes and offers another option in
areas where natural wetlands do not exist or are restricted from use by
environmental protection laws. Constructing a wetlands area where one did not
exist previously can be beneficial in several aspects. Constructed wetlands
offer more potential for operation and design controls than natural wetlands.
Examples of better control through design can be observed in the provision of
liners throughout the system to prevent infiltration/percolation to groundwater,
or providing treatment cells in a marsh, where flow can be terminated in one
cell to facilitate harvesting, while treatment continues in other cells. Artificial
wetlands generally consist of shallow ponds, channels, basins, or trenches
planted with different types of aquatic plant species including bulrushes,
reeds, cattails, coontails, or alligator weeds. Several existing systems as listed
in Table 2.9 have been successfully demonstrated to treat primary and
secondary effluents.
(39)
Small , at Brookhaven National Laboratories experimented with constructed
marsh-pond-meadow systems used to treat raw wastewaters (aerated, screened)
to secondary levels. Two independent experimental systems have been reported
(39 40)
' , one a constructed meadow-marsh-pond, the other a marsh-pond system
treating flows of 12,000 to 40,000 gallons/day. The aquatic processing units
(APUs) of the meadow-marsh-pond system consisted of grassed meadow
overland-flow APU followed by a cattail marsh APU flowing to a pond APU
2-33
-------
Table 2.9
EXISTING ARTIFICIAL WETLANDS API!' s
Lrcaticn
Species Used
Treatment
Objective
Flow
(MGD)
Description
Santee, CA
reeds and
bulrush
treatment of
secondary
effluent
0.1
secondary effluent
applied to reed and
bulrush wetland
Petaluma, CA
Easton, MD
cattail and
bulrush
reed
treatment of
secondary
effluent 0.04
treatment of
lagoon
effluent 0.016
secondary effluent
applied to cattail and
bulrush wetland
secondary effluent
applied to reed
bed
Neshaminy
Falls, PA
cattails
meadow
treatment of
raw wastewater 0.03
screening, aerated
pond, constructed
marsh; oxidation
pond, constructed
meadow in series
Orange County,
NY
variety of
indigenous
species
treatment of
primary
effluent
0.03
2 independent systems
marsh/pond/meadow in
series meadow/pond
marsh in series
2-34
-------
stocked with fish and invertebrates. The system was arranged in series with
recycling options provided among the APUs. The marsh-pond system was
similar, lacking only the meadow. Both systems operated effectively, resulting
in the recommendation of deleting the meadow. Additional research-oriented
artificial wetlands projects that have been terminated are listed in Table 2.10.
Small's work in Brookhaven was used as a guideline in developing a
marsh-pond-meadow system for the Village of Neshaminy Falls,
Pennsylvania . Neshaminy Falls is a mobile home retirement community with
a domestic wastewater flow of 20,000 gallons/day. Following a membrane-lined
aerated basin there are: a 4-cell cattail marsh APU; an intermittantly aerated
pond APU; and a 4-cell overland-flow meadow APU, in series. The marsh,
pond and meadow APUs are lined with bentonite clay overlain with gravel and
sand. Maintenance on the system includes cutting the meadow monthly,
distributing the flow among the four cells of the marsh and the meadow, and
periodically activating the aeration unit in the pond in summer to prevent algae
blooms, and in winter to prevent icing over. The groundskeeper for the mobile
home park is responsible for these tasks.
The marsh-pond-meadow system at Neshaminy Falls has demonstrated
consistently effective reduction of BOD and SS to secondary levels and during
the growing season, treatment to tertiary levels resulting from the uptake of
nutrients by the marsh plants and meadow grasses. Odor and insect problems
have been minimal, and the system has been observed to provide an
environment for several species of birds, fishes and other animals. Figure 2.2
illustrates the effectiveness in removal of several wastewater parameters over a
period of a year and a half.
From the Figure 2.2, it is obvious that a significant problem in controlling the
seasonal variation of nitrogen and phosphorus in the final effluent exists. This
operational problem can be explained by the die back of the wetland vegetation
during the fall, and the consequent decomposition and release of nutrients
during the early part of the year. In spite of this problem, adequate treatment
still takes place resulting from the biological activity of the microorganisms still
active in the root system of the wetland plants. It may be possible to reduce
2-35
-------
Table 2.10
ABANDONED ARTIFICIAL WETLANDS APU'S
Plant (s)
Location Used
Brookhaven, NY
M. Higuel, CA
Greenport, NY
Port Jefferson, NY
Port Charlotte, FL
Westport, CT
Sumter, SC
Cattails
duckweed
Canary grass
Reeds and
bulrushes
Reeds and
bulrushes
Reeds and
bulrushes
Reeds and
bulrushes
Reeds and
bulrushes
Reeds and
bulrushes
Treatment Objective
Mixture of screened
raw wastewator
and septage
Raw sewage
and 2° effluent
Raw sewage
and 2" effluent
Milk bottling
wastewater
2' effluent
2° effluent
2° effluent
Flow
(MGD)
.01
to
.04
.035
to
.025
N/A
N/A
.004
N/A
N/A
Description Reason Cor Abandonment
2 independent systems:
meadow/marsh/pond
marsh/pond Research terminated
Reeds in filter
trench; bulrush
in polishing trench Research terminated
" Research terminated
" Research terminated
" Research terminated
" Research terminated
" Research terminated
N>
I
Ul
-------
Removal Performance for Artificial Wetlands
Aquaculture System, Neshaminy Falls, PA
(April, 1980 - September, 1981)
O Marsh Effluent
. Oxidation Pond
Effluent
D Meadow Effluent
Not Reported
BOD
Total N
f
a
o
n
s
z
rH
*J
3—B
Total P
months
months
months
Figure 2.2
-------
the seasonal variation by cutting back the wetland late in the fall before the
plants can decompose and release the absorbed nutrients.
Among various emergent aquatic plants used in aritifical wetlands, reeds and
•
bulrushes have been experimented with extensively. The hardiness, resistance
to diseases, wider geographical regions, ease of harvesting, tolerance to wider
pH ranges, long growing season, and overwinter capability are reasons for
selecting reeds or rushes for artificial wetland treatment systems. Kathe Seidel
and her co-workers at the Max Planck Institute (MPI) in Germany have been
studying the use of emergent plants for the treatment of waste water since the
early 1950's. A patented system of reeds and rushes (MPI system) grown
hydroponically in gravel and sand trenches is the result of her work at the
(2)
Institute. This system has been patented by Biological Water Purification,
Inc. (BWPI) in the United States. Managed plantings of reeds (e.g.,
Phyragmites spp.) rushes (e.g., Scirpus spp.) have been demonstrated to
reliably provide pH neutralization and removal of BOD, TSS, COD, nutrients,
heavy metals, fecal coliforms, pathogenic bacteria, and some refractory
orgamcs.'2-18'19-41'42'43'
Reeds have an inherently high transpiration rate but a low unit mass of leaves
moderates the overall transpiration rate of reed beds. Biomass production
reported for reeds in the U.S. ranged from 6,540 to 39,900 kg/ha-year. The
combined above ground and below ground production in hydroponic culture
ranges from 230 to 74,010 kg/ha-year in 1- to 3-year old cultures. The
nitrogen removal potential of reeds is 330 to'800 kg/ha-year for the above
(43)
ground mass and 350 to 830 kg/ha-year for the below ground plant mass.
A typical MPI reeds/bulrushes system consists of two groups of shallow
trenches. The first group of trenches are filter trenches each 75 feet long, 12
feet wide, and 4 feet deep, and are filled with a sand layer and three layers of
gravel of ascending gradation. The filter trenches are planted with reeds.
Following the filter trenches are elimination trenches, filled with sand and
gravel in the same manner as the filter trenches, but planted with bulrushes.
Both sets of trenches are operated in series and receive wastewater evenly by
gravity flow.
2-38
-------
Basically, the filter trenches remove a majority of suspended solids through
physical filtration and biological breakdown. The latter is predominently
achieved by microorganisms attached to plant roots and residing in the grave]
or sand medium. It is postulated that active growth of the root system within
the sand or gravel medium prevents clogging of the sand or gravel layers. In
addition, it is hypothesized that some enzymatic excretions by plant roots are
effective in killing some enteric and pathogenic bacteria present in the
wastewater and thus disinfecting the wastewater.
Typical levels of performance by an MPI system are summarized in Table 2.11
for secondary and tertiary treatment.
A hybrid wastewater treatment system consisting of a settling tank in series
with an anaerobic reed (Phragmites communis) treatment cell treating lagoon
Min
effluent was evaluated by Wolverton and compared with a similar system
without the reeds (control system) in a greenhouse with minimum and maximum
temperatures averaging 19°C and 35°C, respectively. The control system
exhibited 62 percent removal of BOD. and the reed system was able to achieve
0
91 percent removal of BOD when hydraulic detention was maintained at 6
0
hours. When the hydraulic detention time was increased to 24 hours, the
control system showed 87 percent and 64 percent removals of BOD and TSS
respectively, while the reed system indicated 96 percent and 96 percent removal
of BOD_ and TSS respectively. The reed system was capable of reducing
ammonia nitrogen from 10.8 mg/1 (influent) to 0.8 mg/1 (effluent), total Kjeldahl
nitrogen (TKN) from 16.4 mg/1 to 3.5 mg/1, and total phosphorus from 4.7 to
2.1 mg/1 after 24 hours of detention.
(41)
Lakshman used cattail (Typha latifolia) and bulrush (Scirpus validus) for
treatment of raw sewage in an indoor summer-lot environment in a static batch
manner. Gravel substrate was used to support the plants. These experiments
demonstrated significant removal of TKN and total phosphorus by both cattail
and bulrush systems. These static experiments indicated that there are
equilibrium levels of removal of nutrients by both cattail and bulrush systems.
Harvesting will promote growth of new plant mass and facilitate further removal
of nutrients.
2-39
-------
Table 2.11
LEVEL OF PERFORMANCE OF REEDS/BULRUSHES
TREATMENT SYSTEM MPI SYSTEM AT LACUNA MIGUEL, CALIFORNIA
(42)
Secondary Treatment
September, 1978
October, 1978
November, 1978
December, 1978
January, 1979
February, 1979
March, 1979
April, 1979
May, 1979
June, 1979
July, 1979
AVERAGE
BOD
87
89
87
86
82
87
85
81
84
83
78
84.5
%
TSS
51
90
90
92
86
91
91
90
86
91
92
90
Removal
COD
80
81
75
78
79
78
78
76
78
77
73
77.5
NH -N
4
52
46
30
25
26
42
24
14
13
14
28.6
Org-N
73
67
54
73
41
-27
50
22
57
40
45.0
TP
15
7
3
9
-14
0
10
11
16
-12
2
4.3
Tertiary Treatment
AVERAGE
54
53
39
50
13
-------
REFERENCES
1. Stowell, R., R. Ludwig, J. Colt and G. Tchobanoglous, "Concepts in
Aquatic Treatment Systems Design", Jour. EED, Proceedings AMSCE,
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3. McDonald, R.C., "Vascular Plants for Decontaminating Radioactive Water
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6. Tridech, S., Trace Contaminant Removal from Secondary Domestic Effluent
by Vascular Aquatic Plants, Ph.D. Dissertation, Tulane University,
March, 1980.
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by Vascular Aquatic Plant Systems," Paper Presented at 1981 Annual
Meeting of American Institute of Chemical Engineers, New Orleans,
Louisiana, November 8-12, 1981.
8. Steward, K.K., "Nutrient Removal Potentials of Various Aquatic Plants",
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Filtration of Sewage", NASA Technical Memorandum No. TM-X-72724,
1975.
10. Boyd, C.E., "Vascular Aquatic Plants for Mineral Nutrient Removal from
Polluted Waters", Jour. Economic Botany, 24, 95(1970).
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"Nutrient Removal by Water Hyacinths", J. WPCF, Jan. 1977 (pp.
57-65).
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Lagoons with Vascular Aquatic Plants", Jour. WPCF, Feb. 1979 (pp.
305-313).
13. EPA, Innovative and Alternative Technology Assessment Manual, EPA
Publication 430/9-78-009, Washington" D.C., Feb. 1980 (Appendix A).
2-41
-------
14. Stowell, R., R. Ludwig, J. Colt, and G. Tchobanoglous, Toward the
Rational Design of Aquatic Treatment Systems, Department of Civil
Engineering, University of California, Davis, California, August,
1980.
15. Culley, D.C., Jr. and Ernest A. Epps, "Use of Duckweed for Waste
Treatment and Animal Feed", Jour. WPCF, Feb. 1973 (pp. 337-347).
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17. Wolverton, B.C., "Engineering Design Data for Small Vascular Aquatic
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18. DeJong, Jr., "The Purification of Wastewater with the Aid of Rush or Reed
Ponds", Biological Control of Water Pollution. J. Tourbier and R. W.
Pierson, Jr., Eds., University of Pennsylvania, Philadelphia, PA pp.
133-137.
19. Spangler, F.L., et al, Wastewater Treatment by Natural and Artificial
Marshes", EPA Publication No. 600/1-76-207, U.S. Environmental
Protection Agency, Ada, Oklahoma, pp. 172 1976.
20. Schwartz, H.G., Jr. and B.S. Shin, "Combined Aquaculture Systems for
Municipal Wastewater Treatment - An Engineering Assessment11,
Aquaculture Systems for Wastewater Treatment, EPA Publication No.
430/9-80-007, June 1980 (pp. 81-103).
21. Coleman, M.S., J.P. Henderson, H.G. Chichester and R.L. Carpenter,
"Aquaculture as a Means to Achieve Effluent Standards", Project
Reports from Hinde Eng. Company, Highland Park, Illinois (undated).
22. Bahr, T.G. and D.L, King, "Municipal Wastewater Recycling: Production
of Algae and Macrophytes for Animal Food and Other Uses",
Development in Industrial Microbiology, Vol. 18, 1977 the Society for
Industrial Microbiology (pp. 121-134).
23. Ryther, J.H., J.C. Goldman, C.E. Gifford, J.E. Huguenin, A.S. Wing,
J.P. Clarner, L.D. Williams and B.E. Lapointe, "Physical Models of
Integrated Waste Recycling-Marine Polyculture Systems", Aquaculture,
Vol. 5, 1975.
24. Hinde Engineering Co., "Little Fish Big Help in Sewage Tretment",
Highland Park, Illinois, (undated).
25. Henderson, S., "Utilization of Silver and Bighead Carp for Water Quality
Improvement", paper presented on the Seminar on Aquaculture
Systems for Wastewater Treatment, University of California, Davis,
CA, September, 1979. pp. 309-350.
26. Henderson, S., "An Evaluation of Filter Feeding Fishes for Removing
2-42
-------
Excessive Nutrients and Algae from Wastewater", Project Report to
U.S. EPA, Robert S. Kerr Environmental Research Laboratory, Ada,
Oklahoma.
27. Binges, R., "A Proposed Integrated Biological Wastewater Treatment
System", in Biological Control of Water Pollution, J. Tourbier and
R.W. Pierson"Jr., editors, University oT Pennsylvania, PA, pp.
225-230, 1976.
28. Las Virgenes Municipal Water District, "Tertiary Treatment with a
Controlled Ecological System", EPA Publication No. 660/2-73-022,
1973.
29. Tchobanoglous, G., and G.L. Gulp, "Wetland Systems for Wastewater
Treatment: An Engineering Assessment", Paper presented at a
Seminar on Aquaculture Systems for Wastewater Treatment, University
of California, Davis, California, September, 1979 (pp. 13 - 42).
30. EPA, "Innovative and Alternative Technology Assessment Manual", EPA
Publication No. 430/9-78-009, Washington, D.C., Feb. 1980 (Appendix
A).
31. Kadlec, R.H., "Wetlands Systems for Wastewater Treatment at
Haughton Lake, Michigan", Aquaculture Systems for Wastewater
Treatment: Seminar Proceedings and Engineering Assessment. EPA
430/9-80-006, Sept., 1979 (pp. 101-139).
32. Williams, T.C. and J.C. Sutherland, "Engineering, Energy and
Effectiveness Features of Michigan Wetland Tertiary Wastewater
Treatment Systems", Aquaculture Systems for Wastewater Treatment:
Seminar Proceedings arid Engineering Assessment. EPA 430/9-80-006,
Sept. , 1979 (pp. 101-139).
33. National Science Foundation, "Putting Wetlands to Work": Mosaic
8(3):25-29, May/June 1977.
34. Fritz, W.R. and S.C. Helle, "Cypress Wetlands for Tertiary Treatment",
Aquaculture Systems for Wastewater Treatment: Seminar Proceeding
and Engineering Assessment, EPA Publication No. 430-9-80-006, Sept.
1979 (pp. 75-81).
35. Fritz, W.R., Personal Communication: Boyle Engineering Corporation,
Orlando, Florida, 1981.
36. Stowell, R., R. Ludwig, J. Colt, and G. Tchobanoglous, Toward the
Rational Design of Aquatic Treatment Systems, Department of Civil
Engineering, University o7California^ Davis, California, August,
1980.
37. Demgen, F.C., "Wetlands Creation for Habitat and Treatment - at Mt. View
Sanitary District, CA", Aquaculture Systems for Wastewater
Treatment: Seminar Proceedings and Engineering Assessment. EPA
430/9-80-006, Sept. 1979.
2-43
-------
38. Small, M.M. "Natural Sewage Recycling Systems", Brookhaven National
Laboratories Number BNL 50630, January, 1977.
39. Small, M.M. and C. Wuran. "Meadow/Marsh/Pond System: Data Report",
Brookhaven National Laboratories, No. BNL 50675, April, 1977.
40. Aquaeulture Site Visit, Mr. George Kohut, Pennsylvania Department of
Environmental Regulation, October, 1981.
41. Lakshman, G., "An Ecosystem Approach to the Treatment of Waste Water",
Jour. Environ, Quality, Vol. 8, No. 3, 1979, pp. 353-361.
42. Pope, P.R., "Wastewater Treatment by Rooted Aquatic Plants in Sand and
Gravel Trenches", EPA Technical Report, Grant No. R-805279,
Moulton Niguel Water District, Laguna Niguel, CA, Feb. 1981.
43. Wolverton, B.C., "New Hybrid Wastewater Treatment Systems Using
Anaerobic Microorganisms and Reeds (Phragmites communis)", paper
presented at Seminar on Innovative Wastewater Treatment Technology,
Louisville, Kentucky, April 23, 1981.
2-44
-------
CHAPTER 3
AMENABILITY OF WASTEWATERS TO
AQUACULTURAL APPLICATIONS
3.0 INTRODUCTION
Prerequisite to an assessment of why aquaculture is not more widely used as a
wastewater treatment method is an identification of the types of wastewaters
potentially amenable to aquaculture treatment. External influences (i.e. climate)
affecting treatment feasibility for a particular wastewater source are not a
factor in assessing amenability. In this case, amenability is synonymous with
treat ability.
In general, wastewaters treatable with biological processes are candidates for
aquaculture treatment. As indicated in Chapter 2, typical domestic wastewaters
and municipal wastewaters have been shown to be amenable to aquaculture
treatment processes. Additionally, certain industrial and agricultural
wastewaters have been shown to be amenable, and others appear to have a
potential for aquaculture treatability.
3.1 Amenability Assessment Methodology
The methodology used in performing the following amenability assessment
involved obtaining a categorization of industrial wastewater sources. The scope
of this survey intended that broad classifications of wastewaters be inventoried
for amenability. It is recognized that the composition of wastewaters can vary
among sources within the same industrial classification and can vary among
individual municipal sources. While actual treatability studies would be
necessary before applying an aquaculture treatment process to a particular
wastewater source, certain generalizations regarding amenability to treatment
are possible.
3-1
-------
As a source of information regarding the typical composition of wastevcaters
characteristic of each industrial classification, reference was made to the U.S.
EPA Guidelines for State and Local Pretreatment Programs. Amenability was
assumed based on a general set of criteria which included the following:
Previous demonstration of amenability in a bench, pilot or full scale
wastewater aquaculture treatment facility;
History of amenability to conventional biological treatment processes or
recommended for biological pretreatment methods in the aforementioned
guidelines;
Minimal pretreatment prior to biological treatment;
Non-excessive chemical/physical pretreatment to remove toxic or corrosive
components and/or non-excessive addition of essential nutrients for
biological sustenance.
Major industrial categories of wastewaters are listed in Table 3.1 together with
the significant pollutants present and treatment history. Those categories
which do not treat wastewaters with conventional biological processes, but
rather with other physical/chemical treatment methods include:
Electroplating, Metal Finishing
Inorganic Chemical Industry
Soap and Detergents
Fertilizer
Iron and Steel
Nonferrous Metals
Phosphate
Steam Electric Power*
Ferro Alloys
Asbestos
Rubber
Water Supply
Paint and Ink Formulating
Steam Supply and Noncontact Cooling*
* Candidate for thermal effluent aquaculture (Chapter 4).
These industrial wastewater categories were eliminated from further amenability
assessment under the assumption that other chemical or physical methods are
more suitable than biological treatment. However, some of these wastewater
categories may become amenable through pretreatment, which might include
removal of heavy metals, temperature reduction, oil and grease removal, pH
adjustment, etc. In addition, those wastewaters which specifically lack
3-2
-------
Table 3.1
SIGNIFICANT POLLUTANTS OF MAJOR INDUSTRIAL CATEGORIES
CFR*
Industry No.
Dairy
Grain Mills
Canned and Preserved
Fruits & Vegetables
Canned and Preserved
Seafood
Sugar
Textiles
Cement
Feedlots
Electroplating
Metal Finishing
Organic Chemical
Industry
Inorganic Chemical
Industry
Plastics S Synthetics
405
406
407
408
409
410
411
412
413
414
415
416
BOD TSS TDS COD pH P
XX XXX
XX XX X X
XX XX
XX X
XXX
XX X
X XX
XX XXX
XX XX
XX XX
XX X
xx x
History**
Oil & Heavy Biological
N Grease Metals Treatment
X X yes
X* yes
X* yes
X yes
X yes
X X yes
X no
X yes
X no
X X yes
X no
x x yes, pretreatment
-------
Table 3.1 (con't)
CFR*
rnd'istry No.
Soap and Detergent
Fertilizer
Petroleum
Iron and Steel
Nonferrous Metals
Phosphate
Steam Electric Power
Ferro Alloys
Leather
Glass
Asbestos
Rubber
Timber
Pulp, Paper,
Paperboard
Builders Paper and
Roofing Felt
Meat Products
417
418
419
420
421
422
423
424
4?5
426
427
428
429
430
431
432
POD
X
X
X
X
X
X
X
X
X
X
X
X
TSS TDS COD pH
X X
X X
X X X X
X
XXX
X X
X XX
XX X
X XX
X X X X
X X X X
XXX
X XX
X
X
X X X X
History**
Oil R Heavy Biological
P N Grease Metals Treatment
X no
XX X no
X X X X yes, pretreatment
XXX no
X X no
X X no
X X X X no
X X no
X X yes, pretreatitient
X XX yes, pretreat.ment
XXX no
X X no
X X yes
X X yes, pretreatment
yes
XXX yes
-------
Table 3.1 (Cont'd)
Industry
CFR*
No.
POL' TSS TDS COD pH
History**
Oil & Heavy Biological
N Crnase Metals Troatmnnt
Water Supply
Food and Beverage
437
438
X X
X X
X
X
no
yep, pretreatment
Misc. Chemicals
439
X
yes
Auto and Other Laundries 444
Paint and Ink 446 &
Formulating 447
Steam Supply S
Noncontact Cooling 449
X
X
yes/no
no
no
en
* Code of Federal Regulations Title 40: parts 425
** U.S. EPA 1977 Federal Guidelines - State & Local Pretreatment Programs, 1977.
-------
nutrients, may be amenable to aquaculture treatment through discharge to a
Publically Owned Treatment Works (POTW), where mixing and blending with
other wastewaters may amend the nutrient deficiency. Nutrient addition could
also be accomplished by combining certain industrial and agricultural
wastewaters. In the case where a POTW contains an APU or is a system of
APU's, an inventory of the industries and their wastewater characteristics
would be necessary to prevent the discharge of toxic or corrosive wastes to the
aquaculture system that may result in process upset.
(2)
An example of a POTW which contains an APU exists in Plant City, Florida .
The 8 MGD activated sludge treatment plant is followed by a water hyacinth
lagoon APU designed for effluent polishing. The following industries contribute
roughly 60 percent of the present flow through the facility:
Pork Processing Plant
Aluminum Extrusion Plant
Candied Fruit Company
Instant Tea Company
Frozen Food Company
Fruit Processor
Ice Cream Plant
Laundromat
Battery Reclamation Plant.
Wastewater derived solely from the aluminum extrusion process would be an
unlikely candidate for wastewater aquaculture, lacking nutrients and containing
significant concentrations of chemical wastes. Through pretreatment and
discharge to the POTW, blending, dilution and nutrient addition take place,
which allows conventional and aquaculture treatment to follow without
interference to the biological system. In fact, the aluminum discharged to the
POTW may be beneficial to the system by facilitating the removal of phosphorus
through precipitation. Those industries remaining from Table 3.1 were assessed
for amenability to aquaculture treatment according to the aforementioned
criteria. Table 3.2 lists the industries assessed, the pollutant characteristics
present, a nutrient assessment and brief discussion by major categories.
Several of the industrial categories listed in Table 3.2 contain wastewaters that
have been tested experimentally in wastewater aquaculture systems. These
include meats and poultry, petroleum refining, pulp mills, photographic and
pharmaceutical industries.
3-6
-------
Table 3.2
Wastewater Amenability for
Aquaculture Uses
I
•sj
wastewa?-.*r Category
Dairy,
Milk. HlUt Product*
Cr«ini
Com (wet)
Com (dry)
wheat
Bulgur
die* (parboiled)
R**dy-To-E«t Cereals
Starch I Gluten
BOO (mg/11
40-10,000
225-7600
6OO-2748
nil
238-521
1280-1305
420-2500
6200-14.633
Suspended Solid*
40-2,000
81-2458
103B-J485
nil
294-414
33-77
80-1573
4,176-14,824
Nutrient
availability
Pi9-210
Nil-US (mg/1)
Pipresent
NtO-10 Cnq/1)
PlO-10 (mg/1)
NlO-10 (1*9/1)
N.0-10 (mg/1)
Pl5.« (ng/1)
N.0-10
P, 30-65 (mg/1)
H.7.0 log/I)
P;Prsssnt
Mi5-30 (mg/1)
PslOO (mg/1)
H! 350-400 (mg/l>
amenability tor Aquaculture Pees
Suitable after BOO removal
Buitttol* after BOD raaoval and
traperature reduction, may be M
deficient
Suitable after BOD reduction, Bay
be K deficient
Unsuitable
Suitable, however high taap and
N-deflclency nay constrain
Suitable after BOD removal, high
temp
Suitable, however aome proceftet
generate high tenperatura wattewater*.
Suitable after BOO and S3
reduction
IVB3TBACT
•Mil dairy and grain Billing indu»t-
riei occur throughout the United Statan.
•owever, the larger, a»ra concentrated
Industrial actlvltie* occur in the aid- '
Meatem grain producing etates. itie
characteriatically high BOO load*
present In waatavaters of the**
Induatrlee «ay conatraln their uae
In aquaculture. High teeiperature
waatewater* resulting froa several
grain •llllfig processes can be be-
neficial to aquaculture systems during
cold weather periods by extending the
treatment process, however it can also
be detrimental by reducing the amount
of dissolved oxygen in the water.
Tsnpereture end BOO reductions end in
soon cases, nutrient addition, can
Improve the amenability of wastawatars
in tha dairy and grain milling
Industries.
Heat* and poultry
Beef Cattle (runoff)
1700
Dairy Cattle (Bilk waste*) 4000
Swine (Mnur*) 2500-20.OOO
Swine (runoff) 100
Sheep c Lasta* (manure) 7000
35,000
2,400
9,000
260
35,000
P.90 (05/1)
N<200 (ng/1)
Ni450 (mg/1)
Pi400
Mi 3000 (sig/1)
Pi 5
Mt 20 (isg/1)
Pt2000 (nj/LI
Hi BOO (ng/1)
Very good potential for
aquacultur* treatment of
wastewaters froa concentrated
feedlot operations. High
aollds and BOO may be inhibiting
to eome system*. Several
waatewatere tried in experimental
aquacultur*. See abstract.
ABSTRACT
Highly concentrated animal feedlots
cannon in western end midwestem statee
produce runoff waatewaters cxtrenoly
high in BOD and suspended solids.
Vaateuatars from both the feddlots
industry and meat packing industries
are amenable to aquarulture treatment,
In most cases only requiring BOD
reduction and grease removal. Ex-
perimental aquaculture has been perfor-
med using swine and poultry wastes C31,
C4| and cattle wastes [5) .
-------
Table 3.2 (con't)
Ul
do
Mastewster Category
(runoff)
Ducks (wet lot)
Meat Products
•laaghterhous* (sisfil*)
Slaughterhouse (eoaples)
Low-Processing
Packing Bouse
High Processing
Peeking House
Satall Processor
Sausage t Luncheon Neat*
Haa Processor
Neat Canner
Canned and Preserved
Fruits and Vegetables
BOP (sg/1)
3000-12,000
500
500-1400
500-1400
$00-1400
500-1400
500-1400
500-1400
500-1400
500-1400
500-5000
Suspended Solids
(•9/1)
8,000
4,000
70-1500
70-150
70-1500
70-1500
70-1500
70-1500
70-1500
70-1500
70-1500
19-24,300
Nutrient
Availability
Pi 80-750 (Bg/l)
Mi 1000 (ng/1)
ft 70 (ng/1)
Kt 50 (•?/!)
P.9.4 («g/l)
lXMil28 Cag/l)
TIOli 114 (•g/1)
Pi 17 (•g/l)
l*Ni68 Cag/D
P:30 (»g/l)
TKNilOS (ag/)
P.70 (sig/1)
TKN:200 («g/l)
Pi 8 (mg/1)
TKNlS
Pl20
TKH.25
Pt 28
1KNi20
P:80
can be nitrogen
deficient
m»n»bility for Aqueculture Pee
Meat product* proceeding
waatewaten may require eoew I
redaction and grease removal.
General acen&bility good.
Highly variable concentrations of
BOD, ss frcei subcategory to
•ubcategory. Excessive BOD and
•uspended aolldi may require
reduction prior to aquaculture use.
ABSTRACT
Seafood processing Industrie* are Boat
comcnly located in coastal areas,
while fruits and vegetables processing
occurs throughout the United States.
Both industrial categories nay re-
quire, reduction in BOD and Suspended
Solids prior to aguaculture treat-
vent, however Host wafltevater* are
amenable. Seafood product processing
wastewaters may require oil and grease
reaovel as well.
-------
Table 3.2 (con't)
w
Wastewater Category BOD (Bg/1)
Canned and Preserved seafood
Crab (Blue, Alaskan, 270-4400
Dungeness)
Shrisf) (Alaskan. Mast Coast 720*2000
Southern)
Claiu, Oysters, Scallops 200-10,000
Finfishes, rich Meal 10O-60OO
Miscellaneous Food and
Beverages
Vegetable Oils 340-60,000
Beverages (alcoholic and 200-5,800
nonalcoholic)
BakerT t Confectionary 400-28,000
Pet Poods 200-12,000
Specialty Products 1,000-6,000
Sugar Processing
Crystalline Cane 13-263
Liquid Cane 72-467
Beet 857
Suspended Solids Nutrient
(HKJ/1) Availability
60-620 good
800-300 good
27-6,000 good
100-5000 good
1.000-57,000 adequate
SO-5,700 adequate
100-5,000 adequate
200-9.000 adequate
UO-1,900 adequate
2-397 TKHsO. 60-1.1
NO -M
59-796 TKlliO.Sl
3,216
enability for Aquaeulture Ose
Suitable providing excessive oil,
grease and BOD reduction
provided
Suitable if oil and grease
pretrestment is available, BOD
reduction may be necessary
Suitable
Suitable with BOD reduction, oil
and grease restoval
Suitable
Suitable with BOD reduction
Suitable if adequate nutrients
available
ABSTRACT
Miscellaneous food and beverage
industries occur throughout the U.S.
while major sugar producing states in-
clude Louisiana, Texas and Hawaii.
Hastevatera from these industries
are generally very amenable to aquacul-
ture treatjaent provided Boo reduction
can be accomplished when necessary and
adequate nutrients are available to
support the aquatic systems.
-------
Table 3.2 (con't)
10
i
wastewater Category
Textiles
wool (•coaxing and
finishing)
Woven C Knit (finishing)
Carpet
Stock c iarn
Laathar Tanning
Tbfcer Product*
pulp and Paper
Builders vap«r and
Hoofing P«lt
pharnaceutlcal
Photographic
PetrolauB Refining
BOO (»9/l)
1OO-8.000
30-1,800
40-500
150-600
1,100-4,000
3-16,000
60-5,000
130-3,000
100-11,000
300
10-800
Suspended Solids Nutrient
<»g/l) availability
15-10,000
1-800
50-120
4-40,000
40-5,000
75-10,000
10-7,000
25
10-300
H/A
H/A
10-50 R/A
1,400-4,000 HCH, 100-600 («•}/!>
PtO-«500
-------
Table 3.2 (con't)
Waatewnter Category BOD (mg/1)
Organic Chemicals 100-500
Auto and Other Laundries 650-1,300
Suspended Solids
(mg/1)
10-4,000
95-5,000
Mutrient
Availability
NH -N 1-1000(mg/1)
N/R
'Amenability for Aquaculture Uses
Metals can be harmful to aquatic
systems. High TDS may constrain
use in aquatic system.
Heavy metals present in some
wastewater categories (Auto Ł
Industrial). Nutrient addition
may be necessary as well as pH
adjustment, oil and grease and
removal'
-------
The category of meats and poultry includes all industries involved in high and
low intensity animal feedlot operations for beef and dairy cattle, swine, sheep,
lambs and poultry. Several feedlot wastewater flows have been proven amenable
to aquaculture treatment in bench and pilot scale investigations. For example,
(3)
poultry and swine wastes have been applied to Tilapia aurea culture ponds ,
swine wastes have been used in the culture of grass, silver and bighead
carp^ , and beef cattle manure has been used to culture duckweed^ . The
recycling of feedlot wastes on-site in a wastewater aquaculture facility provides
an opportunity for the livestock owner to reduce feed costs by harvesting the
aquatic vegetation or organisms and processing them for use in animal feeds.
/c\
Culley and Epps found that wastewater cultured duckweed compared
favorably in terms of nutritional content with conventional animal feeds.
Exxon Company petroleum refinery wastewaters in Baytown, Texas were treated
successfully with water hyacinth APU's, which effectively treated the
(7)
wastewaters even during periods of winter kill. The water hyacinths
harvested from the APU exhibited an abundance of accumulated metals such as
zinc, chromium, molybdenum and nickel. The uptake of metals, phenol and
other contaminants by water hyacinths or other APU macrophytes used to treat
wastewaters in the petroleum industry will undoubtedly constrain the use of the
harvested biomass by-products.
Bench scale wastewater aquaculture has been evaluated for pulp mill effluents at
Weyerhauser Corp. in Washington using the crustacean Moina macrocopa for
(8)
total suspended solids reduction. The organism, which appears seasonally,
was found to reduce the total suspended solids, and when harvested and
assessed for marketability, exhibited the potential for use as a conventional
aquaculture or tropical fish food.
Photographic and chemical wastewaters at the National Space Technology
Laboratories (NSTL) in Bay St. Louis, Mississippi, have been treated
(0)
successfully by water hyacinth APU's. Water hyacinths in this system
demonstrated the capability of accumulating heavy metals.
Pharmaceutical wastes have been used experimentally in wastewater aquaculture
as a food source for Tilapia aurea in the form of spent beer and spent beer
3-12
-------
plus solids. As a food source, the spent beer trials indicated that the
organic materials present in the spent beer were suitable sources of food for
the rearing of Tilapia aurea. While this portion of pharmaceutical wastewaters
are amenable to aquaculture, wastewaters generated in the formulation of other
pharmaceutical products may contain heavy metals or other contaminants in
concentrations not compatible with aquatic biological treatment systems.
Wastewater aquaculture treatment in several other industrial categories may
provide a unique opportunity for the recycling of wastes through the
processing of wastewater aquaculture by-products, and use of those
by-products in animal feeds and feed supplements. For example, particular
grain milling industry subcategories produce wastewaters that appear amenable
to aquaculture treatment. If those wastewaters were applied to a plant or
fish-based APU, the harvested biomass from the APU may be useable as an
animal feed or supplement. It has been suggested that water hyacinths and
other aquatic macrophytes can be dried and ensiled to produce suitable animal
feeds. In addition, fish harvested from an APU may be processed for use
as a protein supplement in animal feeds or used as fertilizer on adjacent
(13)
grain producing croplands.
3-13
-------
REFERENCES
1. U.S. Environmental Protection Agency, Office of Water Program
Operations, 1977. Federal Guidelines to State and Local Pretreatment
Programs. Volumes, I, II and III. EPA-430/9-76-017 a, b, c.
2. Wastewater Aquaculture Site Visit, Plant City, Florida. November 6, 1981.
3. Stickney, R.R. and J.H. Hesby, "Water Quality - Tilapia aurea
Interactions in Ponds Receiving Swine and Poultry Wastes".
Proceedings of the Eighth Annual Meeting of the World Mariculture
Society held at San Jose, Costa Rica. January 9-13, 1977, pp. 55-71.
4. Buck, H.E., R.J. Baur and R. Rose, "Utilization of Swine Manure in A
Polyculture of Asian and North American Fishes". Trans. American
Fish Society, 107:216-222, 1978.
5. Said, M., D.D. Culley, L.C. Standifer, E.A. Epps, R.M. Myers and S.A.
Boney, "Effects of Harvest Rate, Waste Loading, and Stocking
Density on the Yield of Duckweeds." Proc. World Maricul. Soc.
10:769-780, 1979.
6. Culley, D.D. and E.A. Epps, "Use of Duckweed for Waste Treatment and
Animal Feed." Journal of the Water Pollution Control Federation.
45(2):337-347, 1973.
7. Chambers, G.V., "Performances of Biological Alternatives for Reducing
Algae (TSS) in Oxidation Ponds Treating Refinery/Chemical Plant
Wastewater." Paper Presented at the 51st Annual Conference of the
Water Pollution Control Federation, 1978.
8. Norman, K.E., J.B. Blakely and K.K. Chew, "The Occurrence and
Utilization of the Caldoceran Moina macrocppa (Straus) in a Kraft Pulp
Mill Treatment Lagoon." Proc. World Maricul. Soc. 10:116-121, 1979.
9. Wolverton, B.C. and R.C. McDonald, "Wastewater Treatment Utilizing
Water Hyacinths". Paper presented at the National Conference on
Treatment and Disposal of Industrial Wastewaters and Residues,
Houston, 1977.
10. Kohler, C.C. and F.A. Pagan-Font, "Evaluation of Rum Distillation Wastes,
Pharmaceutical Wastes and Chicken Feed for Rearing Tilapia aurea in
Puerto Rico". Aquaculture 14:339-347, 1978.
11. Robinson, A.C., H.J. Gorman, M. Hillman, W.T. Lawhon, D.L. Moose and
T.A. McClure, "An Analysis of the Market Potential of Water
Hyacinth-Based Systems for Municipal Wastewater Treatment." Batelle
Columbus Laboratories, Columbus, Ohio N-76-28679, 1976.
3-14
-------
12. Henderson, S., "Utilization of Silver and Bighead Carp for Water Quality
Improvement," Aquaculture Systems for Wastewater Treatment:
Seminar Proceedings and Engineering Assessment, EPA Publication No.
430/9-80-006, Sept. 1979 (pp. 309-349).
13. Personal Communication. Bill Wolf, Necessary Trading Company, New
Castle, Virginia. November 18, 1981.
3-15
-------
CHAPTER 4
GEOGRAPHICAL VARIABLES WHICH AFFECT UTILIZATION
OF AQUACULTURE TECHNOLOGIES
4.0 GENERAL
In addition to the characteristics of wastewater flows which prescribe their
amenability to aquaculture treatment, a series of environmental variables also
influence aquatic wastewater treatment systems. These variables are generally
climatological and hydrogeological in nature. Table 4.1 summarizes the
pertinent variables of each group. In order to address fully the impact of
these variables on parameters such as geographic location, design, operation
and maintenance, each variable is discussed relative to wastewater aquaculture
in this chapter.
The environmental requirements of aquatic treatment species have been
intensively investigated and reported in a series of four publications for the
California State Water Resources Control Board. Because many of the
environmental requirements discussed are a function of climatological and
hydrogeological conditions, these publications are excellent references for
specific species information.
4.1 Climatological Variables
4.1.1 Solar Insolation
Solar energy, the driving force of photosynthesis, is essential to the aquatic
animals, plants, algae and microorganisms which inhabit a .wastewater
aquaculture treatment system. In aquatic environments, the amount of solar
energy available affects the rate of photosynthesis, thus the oxygen supply, pH
4-1
-------
Table 4.1
CLIMATOLOGICAL AND HYDROGEOLOGICAL
VARIABLES AFFECTING AQUACULTURE
Climatological Variables
Solar Insolation
Temperature
Precipitation
Evaporation/Transpiration
Wind
Heating and Cooling Degree Days
Hydrogeological Variables
Instream Flow
Surface Runoff
Flood Potential
Groundwater Availability
Natural Wetlands Proximity
4-2
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and carbonate concentration, and the rate of evaporation and
evapotranspiration.
Solar insolation values are important in determining the quantity of activation
energy available in an aquatic treatment system to accomplish photosynthesis.
Photosynthetic reactions are primarily responsible for the removal and uptake of
macronutrients (nitrogen and phosphorus) by aquatic plants and animals. Thus
solar energy drives an essential part of the wastewater treatment process. In
northern latitudes, the influx of solar energy may not be seasonally sufficient
to maintain adequate photosynthesis rates.
In summary, the quantity of solar energy entering an aquatic system is a
stimulant essential to the plants and animals inhabiting the system and it is
often a limiting factor. Table 4.2 illustrates this concept by demonstrating the
probable yield of algal mass from a typical municipal wastewater treated by an
optimally designed and operated algae aquaculture treatment system based on
naturally available sunshine. It is apparent that an aquaculture treatment
system in lower latitudes can be more effective than a similarly designed system
at higher latitudes.
4.1.2 Temperature
Ambient temperature is affected by the solar insolation availability in a given
area and varies with latitude. Mean temperature, in combination with other
climatological parameters dictates the evaporation and evapotranspiration
potential at a given locality. Ambient temperature, like solar energy undergoes
diurnal and seasonal variation. Heating and cooling degree days are an
effective expression of the annual variation in ambient temperature. In a
broader sense, heating/cooling degree days for a given locality can be used
effectively to estimate the length of growing season for a given aquatic species.
The life associated with the aquatic environment in any location has its species
composition and activity regulated by water temperature. Since essentially all
of the organisms in wastewater aquaculture facilities are "cold blooded" or
poikilotherms, the temperature of the water regulates their metabolism and
(3)
ability to survive and reproduce effectively. Temperature, is a catalyst, or
4-3
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Table 4.2
Range of Probable Yield of Algae From a
Properly Designed Algae Aquaculture System (Ib/ac-day)
LATITUDE
Deg. N or S
0 "ax
Min
10 Max
Min
20 Max
Min
30 Max
Min
40 Max
Min
50 Max
Min
60 Max
Min
Jan
54.0
50.4
53.5
43.0
43.9
32.2
32.6
18.2
19.2
7.2
6.7
2.4
1.7
0.5
Feb
63.8
52.6
58.6
44.2
51.1
33.6
42.2
23.0
31.2
12.7
16.8
4.6
7.7
1.0
Mar
65.0
49.4
63.4
46.3
59.0
40.3
52.3
32.2 .
43.4
77.8
33.8
13.9
25.7
7.9
Apr
63.8
45.1
65.0
43.9
65.0
40.8
62.6
36.2
43.4
30.0
50.4
23.3
42.2
19.0
May
59.8
43.7
64.8
46.1
68.2
46.7
69.6
44.2
68.6
38.7
65.0
24.6
59.8
31.7
Jun
56.6
24.7
62.9
31.0
68.2
35.5
71.0
39,1
71.5
41.5
71.3
42.2
70.6
41.8
Month
Jul
57.1
32.9
63.6
37.9
67.7
41.3
69.4
42.7
69.1
41.3
67.2
37,2
64.3
34.6
Aug
60.5
40.1
63.9
42.2
65.3
42.3
65.0
39.0
61.9
35.3
67.2
30.0
49.2
24.0
Sep
64.5
49.7
63.9
47.0
60.5
42.2
55.4
35.3
48.7
26.9
39.8
17.5
30.2
9.1
Oct
63.6
48.7
59.5
43.4
53.8
36.0
46.1
27.1
36.5
17.3
24.0
9.6
10.2
6.2
Nov
61.4
48.5
54.7
42.2
45,6
33.1
35.5
21.6
22.8
10.1
9.2
3.6
2.4
0.7
Dec
60.7
46.8
54.0
38.9
43.7
28.8
30.2
16.1
15.8
5.8
6.2
1.7
1.2
0.2
Note: Computed values derived from McGaughey^2'
-------
depressant, an activator, a restrictor, a stimulator, a controller, and a killer,
and is therefore one of most influencial variables to wastewater aquaculture.
Temperature determines the growth conditions of aquatic species in an
aquaculture treatment system, and also dictates aeration requirements.
Temperature also affects the self-purification phenomenon in water bodies and
therefore the aesthetic and sanitary qualities that exist. Indicator enteric
bacteria, and presumably enteric pathogens, are likewise affected by
temperature. It has been shown that both total and fecal coliform bacteria die
(4)
away more rapidly in the environment with increasing temperatures. This
effect has great implication in the design of an aquaculture treatment system,
since it offers a potential mechanism to control by-product contamination by
microorganisms.
Temperature changes in water bodies can alter species variety and dominance in
the aquatic community. The aspect of temperature as a variable influences to a
great degree the selection of aquatic species for an aquaculture treatment
system and the requirements for pretreatment such as cooling or heating of
wastewaters. Several methods have been successfully applied to remedy
off-season temperature problems inherently associated with certain aquaculture
treatment processes. These methods include:
Storage of wastewater during cold weather periods and application to the
aquaculture treatment system during periods when the temperature permits.
Provision of a greenhouse to maintain system temperature within a desirable
range for aquatic species growth and maintenance.
Supplemental with thermal effluents from power plants or industrial boilers.
There are currently no known wastewater aquaculture facilities which use
thermal waste heat effluents to maintain active populations of aquatic species
during cold weather periods to continue the treatment process. There are
however, several "clean" water aquaculture facilities throughout the United
States which utilize thermal power plant effluents to extend the growing season
of cultured aquatic species. A number of aquaculture facilities that practice
thermal aquaculture at power plant sites are listed in Table 4.3. The
experience gained through aquaculture research in the power generating
4-5
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Table 4.3
THERMAL AQUACULTURE FACILITIES
Location
Public Service Electric
and Gas Co., Mercer
Generating Station, NJ
Tennessee Valley Authority,
Brown's Ferry Nuclear Plant,
Athens, AL
Astro-Marine Industries,
Hawaii
So. Carolina Public Service
Authority, Santee Cooper,
South Carolina
Pennsylvania Power & Light,
Pennsylvania
Southern California, Edison
Ventura Los Angeles,
Species
tilapia,
trout
tilapia
golden
tilapia
tilapia,
ells,
catfish
channel
catfish
lobster,
abalone
Comment
Demonstration with thermal
Experimental thermal
Experimental with thermal
Full scale with tilapia
experimental with catfish
Current expanding pilot
facility
2 coastal power plants, one
demonstration, the other bench
scale
Tennessee Valley Authority,
Gallatin Power Plant,
Tennessee
Basin Electric Power Coop.
Leland Olds Station,
North Dakota
trout,
catfish
trout
N/A
Commercial Scale
4-6
-------
industry may be of value in wastewater aquaculture systems located in northern
climates.
4.1.3 Precipitation
Precipitation takes many forms including rain, snow, hail, glaze (freezing rain)
and ice pellets. Excessive rain may result in some undesirable effects on
aquaculture treatment systems. These effects may include:
Dilution of wastewater to the extent that is no longer compatible with
certain aquaculture treatment systems.
Short-circuiting of the wastewater resulting in inadequate treatment and
resuspension of settled solids.
Erosion and/or siltation of certain aquaculture treatment systems due to
excessive runoff resulting from precipitation.
Flooding or undesirable inundation of certain aquaculture treatment
systems.
The annual variation in quantity and type of precipitation in a given area
should be considered in the design of an aquaculture treatment system. Some
aquatic species are vulnerable to one form of precipitation or another. For
example, natural aquaculture systems using floating plant species such as
duckweed or water hyacinth are vulnerable to washout by excessive rain and
runoff. In addition, the low pH of rainfall in certain northern areas of the
United States can be detrimental to aquatic plants and animals in an aquaculture
system. Precipitation in the form of snow, hail, glaze or ice pellets in general
is harmful to aquaculture treatment systems and should be considered as part of
planning and design efforts.
4.1.4 Evaporation and Evapotranspiration
Evaporation is influenced by physical parameters of the ambient environment
such as air temperature, water temperature, humidity, barometric pressure,
windspeed, solar insolation. Local evaporation potential infJuences the
predominant aquatic species in a given locality. Use of an aquatic species from
coastal zones in an arid region may present adaptation problems in terms of
evaporation potential in addition to other climatologieal variables. Excessive
4-7
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evaporation rates may result in dessication of plants and effect their growth.
In addition, evaporative losses may result in increased concentrations of salts
and/or other pollutants which may in turn affect the performance of an
aquaculture treatment system. From a physical standpoint, evaporation can be
beneficial in terms of pretreatment of the wastewater prior to discharge to an
aquaculture treatment system. For example, thermal wastewaters can be cooled
by evaporation so that the wastewater may become amenable to a given
aquaculture system. Evapotranspiration is a biological process accomplished by
plants which varies greatly among aquatic species.
The rate of evapotranspiration can be used as a gauge to measure the growth
rate of an aquatic plant. For example, water hyacinths characteristically
maintain a high evapotranspiration rate and are thus rapid growing plants when
environmental conditions are optimal. It has been estimated that the
evapotranspiration rate can be as high as 1.5 to 3 times the evaporation rate
for certain aquatic plants.
4.1.5 Wind
Wind facilitates air circulation and thus increases the air/water interface and
consequently, the evaporation potential. When other environmental conditions
are optimal, a slight wind may aid the performance of a plant-based wastewater
aquaculture system by increasing evaporation and evapotranspiration potentials.
On the other hand, constant excessive winds may interfere with an aquaculture
system using floating aquatic plants such as duckweed or water hyacinth by
driving the plants ashore and encouraging uneven distribution of the species
across the pond surface. Strong winds during low temperature periods may
result in excessive wind chilling, which affects the performance of rooted
aquatic species such as reeds, bulrushes and cattails. In areas where
excessive wind may be a constraint, the use of wind breaks can be considered
in facility design to mitigate undesirable effects. In addition, narrow or small
ponds can be constructed to minimize wind effects.
4.2 Hydrogeological Variables
4.2.1 Instream Flow, Runoff and Flooding
4-8
-------
Instream flow is an important variable when natural water bodies and natural or
constructed wetlands are used as a means of treating wastewater. Instream
flows vary according to the area of drainage, the amount of groundwater
recharge and precipitation, and other hydrological variables. Excessive
instream flow may result in erosion or even destruction of an aquaculture
treatment system based on a natural water body or wetland. Insufficient
instream flow may also affect the performance of an aquaculture treatment
system and reduce its efficiency. In addition, seasonal fluctuations of instream
flow may be well-suited for one aquatic species but detrimental to another.
Abnormally intense precipitation may result in large volumes of runoff and
instream flow beyond the carrying capacity of the stream and may result in
flooding. Excessive runoff and flood waters may dilute wastewater being
treated by the wetland-based aquaculture treatment system and degrade the
treatment performance. Flood waters can also be detrimental structurally to
wetland-based aquaculture treatment systems due to the intense erosion
potential. Flood trails can leave or re-deposit debris or solids on an
aquaculture treatment system and render it inoperable.
Runoff waters are highly variable in amount and types of pollutants.
Depending on location, runoff may contain toxic pollutants which can be harmful
to aquatic plants and animals.
4.2.2 Groundwater
In areas where a significant portion of stream flow is comprised of groundwater
discharge, fluctuations of the groundwater table and/or depletion of the
groundwater source become an important variable in selecting and designing an
aquaculture treatment system based on a natural water body or wetland.
Extensive groundwater depletion may result in a lowering of the groundwater
table so that it can no longer support the aquaculture treatment system. In
addition, groundwater depletion may encourage the intrusion of salt water,
thereby upsetting the dissolved solids concentration of the system and
potentially reducing the performance of the aquaculture treatment system due to
increased salinity. Groundwater availability is highly variable and should be
4-9
-------
understood fully before an aquaculture treatment system can be successfully
designed and operated for a specific facility site.
4.2.3 Natural and Artifical Wetlands
Wetland environments under proper management can be used effectively for the
treatment and renovation of certain wastewaters. The capability of these
unique environments to treat wastewaters can be attributed to the high rate of
productivity and nutrient recycling" characteristic of wetland settings. Utilizing
constructed or natural wetlands in the place of conventional systems can be
economically and environmentally attractive. Natural wetlands that have been
damaged either directly or indirectly by human activity offer potential sites for
wastewater aquaculture facilities. The nutrient input and protection afforded
by controlled wetlands aquaculture can help promote recovery of damaged
wetlands.
There are many types of wetlands and pollutant removal efficiencies vary with
type and location of wetlands. There are various classifications of wetlands and
it is not the purpose of this study to select one classification scheme over
another. For national needs, a classification system was developed in 1979 by
U.S. Fish and Wildlife Service with four long-range objectives: (1) to
describe ecological units that have certain homogeneous natural attributes; (2)
to arrange these units in a system that will aid decisions about resource
management; (3) to furnish units for inventory and mapping; and (4) to
provide uniformity in concepts and terminology throughout the United States.
According to this wetland classification system, wetlands are defined as: "lands
transitional between terrestrial and aquatic systems where the water table is
usually at or near the surface or the land is covered by shallow water.
Wetlands must have one or more of the following three attributes: (1) at least
periodically, the land supports predominantly hydrophytes; (2) the substrate is
predominantly undrained hydric soil; and (3) the substrate is nonsoil and is
saturated with water or covered by shallow water at some time during the
growing season of each year". The U.S. Fish and Wildlife Service is preparing
a list of hydrophytes and other plants occurring in wetlands of the United
States. The U. S. Soil Conservation Service is preparing a preliminary list of
hydric soils for use in this classifications scheme.
4-10
-------
Basically, wetlands have been classified into five systems namely: the Marine,
Estuarine, Riverine, Lacustrine, and Palustrine Systems and contain a
hierarchical progression of subsystems classes, and subclasses. Modifiers for
water regime, water chemistry, and soils are applied to classes, subclasses, and
dominance types. Special modifiers can be used to describe wetlands and
deepwater habitats that have been either created or highly modified by man or
animals. This classification system with modifiers can be used to provide
preliminary suitability evaluations of a particular local wetland for an
aquaculture treatment system.
Soil is one of the most important physical components of wetlands. Through its
depth, mineral composition, organic matter content, moisture regime,
temperature regime, and chemistry, it exercises a strong influence over the
types of plants that live on its surface and the kinds of organisms that dwell
within it. For wetlands, the most basic distinction in soil classification in the
United States is between mineral soil and organic soil.
In order to facilitate identification of natural wetlands for aquaculture treatment
of wastewaters, the geographical distribution of wetlands should be known.
The U.S. Fish and Wildlife Service has completed a wetlands inventory and
mapping for the eastern United States and is currently engaged in similar
mapping for Alaska, and eventually will produce 7i minute wetland maps for the
entire United States. The maps are too large for inclusion in this study but
are mentioned for reader awareness.
Wetlands can be effectively used to treat waste water, if they are properly
selected, designed, operated, and managed. Among the many mechanisms
involved in a wetland system which contribute in varying degrees to the
treatment and renovation of wastewater are microbial degradation/stabilization,
sedimentation, chemical precipitation, filtration, coagulation, bio-filtration into
groundwater, plant metabolism, etc. Understanding these mechanisms and their
effectiveness in treating wastewater by wetland aquaculture systems is important
before these types of systems can be cost-effectively designed and made
environmentally acceptable. As mentioned elsewhere in this study, much of the
current aquaculture research is being directed toward better understanding of
artificial wetland systems.
4-11
-------
4.3 Summary
There are a wide range of variables which influence the selection, planning,
design, and successful operation of wastewater aquaculture facilities. These
variables are not well-documented for wastewater aquaculture. It would be
helpful to future planners of such systems to have elimatological,
hydrogeological, and biological documentation as mentioned here in a design
manual format.
4-12
-------
REFERENCES
1. The California State Water Resources Control Board. 1979. The Use and
Potential of Aquatic Species for Wastewater Treatment.
Appendix A: The Environmental Requirements of Aquatic Plants
Appendix B: The Environmental Requirements of Fish
Appendix C: The Environmental Requirements of Crustaceans
Appendix D: The Environmental Requirements of Freshwater Bivalves
Appendix E: The Use of Aquatic Systems for Wastewater Treatment: An
Assessment, (in progress)
2. McGauhey, PH., 1968. Engineering Management of Water Quality, McGraw-Hill,
New York.
3. United States Environmental Protection Agency. 1976. Water Quality Criteria.
4. Ballentine, R.K. and F.W. Kittrell, 1968. Observations of Fecal Coliforms in
Several Recent Stream Pollution Studies. Proceedings of the Symposium on
Fecal Coliform Bacteria in Water and Wastewater, May 21-22, 1968, Bureau
of Sanitary Engineering, California State Department of Health.
5. United States Department of the Interior Fish and Wildlife Service, 1979.
National Wetlands Inventory, Wetlands Classification, 1979.
4-13
-------
CHAPTER 5
INSTITUTIONAL AND FINANCIAL DETERRENTS
TO WASTEWATER AQUACULTURE
5.0 GENERAL
Among the factors which can influence the application of wastewater aquaculture
technologies are certain institutional and financial constraints. Institutional
constraints include policies, regulations and laws which either limit the
application of wastewater aquaculture technologies or contribute to the costs of
wastewater aquaculture facilities in a way that causes them to be less
competitive than other alternatives. This chapter highlights some of the more
major institutional and financial deterrents to wastewater aquaculture in the
United States. It should be noted that two recent reports prepared under
sponsorship of the U.S. Joint Sub-Committee on Aquaculture address regulatory
constraints and certain financial aspects of the aquaculture industry in the
(1 2)
United States. ' The publications focus on clean water aquaculture for the
purpose of food production and give little attention to aquaculture as a
wastewater treatment process. The reader is referred to them for additional
information on these topics.
5.1 Clean Water Act of 1977 (P.L. 95-217)
One of the current laws which encourages the use of wastewater aquaculture is
the Clean Water Act of 1977. This law provides financial incentives to
authorities responsible for publically owned wastewater treatment works to
investigate and implement wastewater technologies which meet certain U.S. EPA
criteria under the definition of "innovative" and "alternative" (I/ A)
technology.
5-1
-------
Section 201, part d(l) of the Clean Water Act promotes the construction of
revenue producing facilities which reuse/recycle pollutants under the federally
funded construction grants program, Aquaculture systems have demonstrated
this ability. In addition, Section 201, part g(5) requires that recipients of
Federal grants investigate innovative and alternative wastewater treatment
techniques before additional Federal grant funding is made available for design
or construction of any publicly owned treatment works (POTW). The Act
provided financial incentives for I/A technologies including wastewater
aquaculture prior to October 1, 1981. These financial incentives were extended
by PL 97-117 and include:
Wastewater aquaculture processes were eligible for up to 85 percent federal
funding (10 percent more than conventional technologies for facilities
construction);
15 percent cost-effectiveness preference for aquaculture processes over
the least costly conventional technology; and
100 percent funding to modify or replace an innovative/alternative
technology system in the event of failure.
Experience indicates that there has been reluctance by various State regulatory
agencies with approval authority for wastewater facilities to accept designs for
facilities which incorporate innovative or alternative technologies, including
aquaculture. Although P.L. 95-217 provides certain incentives for use of I/A
technologies, engineers are often reluctant to propose such systems because
they must then engage in a complex project approval process and often
encounter delays in obtaining approvals. This process often involves educating
regulatory agency staff and conformance with various procedures for obtaining
special exceptions and exemptions, both of which tend to deter engineers.
Additionally, engineers who are aware of aquaculture and other 11A technologies
are frequently reluctant to suggest or design such technologies to potential
increased exposure to design risk and legal claims. Although EPA grant funded
projects offer replacement guarantees in the event of facility failure, the
accompanying administrative difficulties and costs are a significant deterrent.
Experience has shown also that municipalities and other public bodies are often
reluctant to accept recommendations for I/A technology, such as aquaculture,
5-2
-------
when it is perceived that they may be "guinea pigs" for something that is
relatively untested.
P.L. 95-217 also recognizes the value of facilities which culture plants and fish
for beneficial uses other than wastewater treatment and provides for National
Pollutant Discharge Elimination System (NPDES) permits for such facilities.
5.2 National Aquaculture Act of 1980 (P.L. 96-362)
The National Aquaculture Act of 1980 makes it a national policy to encourage
(4)
development of aquaculture in the United States. The Act calls for a
National Aquaculture Development Plan to be used in overcoming many of the
obstacles encountered in aquaculture development. The Act authorizes federal
funds for aquaculture development to be allocated by Congress and the Office
of Management and Budget.
The Joint Subcommittee on Aquaculture (under the Federal Coordinating Council
of Science, Engineering, and Technology) was formally introduced in this Act to
increase the overall effectiveness and productivity of federal aquaculture
research, technology transfer, and assistance programs. Currently, three
panels comprise the Joint Sub-Committee: Economics, Science and Technology,
and Education and Training,
5.3 Food and Drug Cosmetic Act (FDCA)
The Federal Food and Drug Cosmetic Act (FDCAr and Fair Packaging and
(1 fi^
Labeling Act were promulgated to protect humans and animals from
consuming unhealthful foods. These regulations would apply to any by-product
of a wastewater aquaculture facility that is intended for human consumption.
The regulations prohibit the distribution of articles that are adulterated
(unsafe, filthy) or misbranded (false or misleading advertising). The Delaney
amendment to the FDCA bans any additive that induces cancer when ingested
by human or animals.
One serious public health concern is the bioaccumulation of heavy metals and
toxic substances in both plants and animals reared in wastewater aquaculture
5-3
-------
facilities. Another is the transfer of viruses and disease through other
microorganisms present in wastewaters that become associated with harvested
by-products. By severely restricting the ultimate disposition of waste water
aquaculture by-products, the potential economic benefits are also diminished and
this may be sufficient to deter selection of aquaculture for a particular
application. At best, the current Food and Drug laws severely limit potential
re-use and recycle applications of aquaculture by-products for human use.
An example of a project affected by these restrictions is the Benton, Arkansas
fish aquaculture treatment facility. Neither the FDA nor other State and local
health agencies have allowed distribution of fish reared at this facility for
human consumption although the fish were grown under highly controlled
(17)
conditions.
5.4 Sludge Management Regulations
The U.S. EPA is developing regulations which address distribution and
marketing of sewage sludge products under 40 CFR Parts 257 and 258. The
EPA has recognized a need to protect the public from toxic substances and
pathogens that may be present in sludges and sludge by-products that are
distributed and marketed. In addition, EPA is attempting to encourage
resource recovery through beneficial uses of sludges and sludge by-products as
fertilizers and soil conditioners by controlling unsafe sludge distribution and
marketing practices. Although the regulation does not specifically address
wastewater aquaculture by-products, such as fish, fish emulsions, composted
plant materials, etc., which have potential uses as fertilizers and soil
conditioners, these products are analogous to sludges from conventional
treatment facilities. The regulations govern the placement of stabilized sludge
in acceptable areas and provides minimum quality requirements for sludge that
is to be landspread on food chain cropland. The quality requirements are in
terms of cadmium, polychlorinated biphenols (PCB's), lead and pathogenic
organisms.
The regulations do not apply to agricultural waste such as manures and crop
residues returned to the soil as fertilizer or as a soil conditioner, but do apply
5-4
-------
protect the facilities against flood damage and discharge of untreated wastes.
Wetlands facilities, by their very nature are sited and constructed in areas
subject to flooding and would be in conflict with these Agency rules. Although
Section 318 of the Clean Water Act specifically allows the granting of permits
for aquaculture facilities in navigable waters, it is logical to expect that such
facilities would face strong local opposition. It is believed that a Section 318
discharge permit has yet to be issued for an aquaculture facility.
5.8 Financial Considerations Influencing Wastewater Aquaculture Development
One of the more serious problems facing all wastewater treatment projects,
aquaculture and conventional, is funding. The U.S.EPA Municipal Construction
Grants Program has benefited many publically owned treatment facilities but
does not provide assistance to solve industrial or agricultural wastewater
problems. The EPA construction grants program has funded up to 85 percent
of the construction cost of wastewater projects incorporating
innovative/alternative technologies with the state and local share being 15
percent. This program has funding policies that encourage wastewater
aquaculture because of opportunities to conserve energy and recycle wastes.
There is a particular financial incentive due to the fact that grant funds are
only available for design and construction of facilities while the burden of
operating costs is always a local matter. The incentive to use of aquaculture
stems from a comparatively low energy costs which must be borne locally for the
life of the facilities.
Privately owned wastewater treatment facilities, such as an industrial treatment
plant, must be financed by the industry. In certain cases, the Federal Small
Business Administration can assist small businesses with the financing of
wastewater facilities that are required as the result of water pollution control
laws/ However, for technologies like aquaculture which are relatively
untested, there may be a lack of confidence by such funding sources and a
tendency to use more conventional approaches. Additionally, smaller businesses
may be reluctant to commit the comparatively greater time and financial
resources that would be necessary to gain approval of wastewater facilities
which are still considered experimental.
5-7
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The Farmers Home Administration has, in the past provided loans and grants
for waste disposal facilities in rural area communities (less than 10,000
population) if these communities can not obtain reasonable credit from other
sources. The loans are typically for 40 year terms; grants can cover up to
75 percent of eligible project costs. The Economic Development Administration
can help fund public works in areas of high unemployment and where economic
growth is lagging.
The prospect of selling wastewater aquaculture by-products has potential
attractiveness and may at some future time become more of an incentive to use
of aquaculture processes. For example, the Woods Hole Oceanographic Institute
tested a marine aquaculture system using secondary wastewater as a nutrient
source for a plankton-bivalve mollusk food chain. Reported estimates of
production indicate that a town of 50,000 persons with a 126 acre wastewater
aquaculture treatment system could grow over 900 tons of oysters annually with
(22)
an estimated value of over $85 million as a luxury food. Fish raised to
remove algae from waste treatment lagoons at Quail Creek, Oklahoma have been
estimated to be able to provide a potential return of approximately 2 cents/1,000
gallons of wastewater treated.
However, such returns are only "potential" at this time due to previously
discussed restrictions which prevent human consumption of waste-grown aquatic
organisms. Other users are constrained by processing requirements, and still
others may provide ready economic returns with little or no processing
requirements. By-product processing requirements and potentials are further
discussed in Chapter 8.
5.9 Summary
There are a number of Federal and State policies, laws, and regulations which
are intended to encourage low-energy wastewater systems and systems which
have a potential for recycling resources. The most important of these are the
Clean Water Act and the National Aquaculture Act which favor wider
implementation of wastewater aquaculture. Other laws, the most significant of
which is the Food, Drug, and Cosmetic Act are considered restrictive of
wastewater aquaculture due to restrictions on by-product utilization, which if
5-8
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amended, could provide significant financial incentive for more widespread
application of the technology.
Wastewater aquaculture cannot be fully exploited for its potential benefits until
there is a coordinated effort to gain exceptions to current restrictions. Under
appropriate controls on by-product quality and stringent monitoring of
wastewater aquaculture operations, it is believed that the technology can fulfill
a two-fold purpose of producing clean water while also providing safe,
acceptable, marketable by-products.
5-9
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REFERENCES
1. U.S. Fish and Wildlife Service, "Aquaculture in the United States;
Regulatory Constraints", 6 volume report prepared by Aspen System
Corp., Washington, B.C. 20240 (1981).
2. Wharton Applied Research Center, "A Study to Examine the Capital
Requirements of the United States Aquaculture Industry", Univ. of
PA, Philadelphia, PA 19104 (1981).
3. Title 33 U.S.C. 466 et seq.
4. Title 16 U.S.C. sect. 2801-2810
5. Title 42 U.S.C. sect. 4321 et seq.
6. Title 7, 15, 16 U.S.C.
7. Bille Hougart, Personal Communication (1981),
Chairman Joint Subcommittee on Aquaculture.
8. Federal Register, Vol. 39 No. 115 (1974).
9. Federal Register Vol. 45 No. 98 (1980).
10. Lowell Keup, U.S. Fish and Wildlife Service, Personal Communication
(1981).
11. Gloyna, E.F. and L.F. Tischler, "Recommendations for Regulatory
Modifications, The Use of Waste Stabilization Pond Systems", JWPCF,
Vol. 53, No. 11 (1981).
12. Title 16 U.S..C. sect. 1531.
13. O'Brien, W.J., "Use of Aquatic Macrophytes for Wastewater Treatment",
Journal of the Environmental Engineering Division-Proceedings of the
ASCE, Vol. 107 No. EE4 (1981).
14. Florida Administrative code, Chapter 17-4(a).
15. Title 21 U.S.C. sect. 346A.
16. Title 15 U.S.C. sect. 1457 et seq.
17. Scott Henderson, Arkansas Game and Fish Commission, Personal
Communication, (1981).
18. Henderson, S. "An Evaluation of Filter Feeding Fishes for Removing
Excessive Nutrients and Algae from Wastewater", prepared for U.S.
EPA, Ada, OK (1981).
19. Federal Register Vol. 44 No. 179 (1979).
20. Title 42 U.S.C. sect. 6901 et seq.
5-10
-------
21. Federal Register Vol. 45 No. 39 (1980).
22. Office of Management and Budget "Catalogue of Federal Domestic
Assistance", Government Printing Office, Washington, D.C. 20402
(1981).
23. Suffern, J.S. C.M. Fitzgerald and A.T. Szluha, et al, "Trace Metal
Concentrations in Oxidation Ponds", JWPCF, Vol. 53, pp. 1609-1619,
1981.
5-11
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CHAPTER 6
DESIGN AND OPERATION OF AQUACULTURE TREATMENT FACILITIES
6.0 INTRODUCTION
An extensive study report (National Operation and Maintenance Cause and
Effect Survey) by the U.S. EPA, indicated that the majority of existing
conventional wastewater treatment plants can not meet optimal levels of
performance as intended. This performance inefficiency was attributed to two
factors: (1) general lack of process understanding by operations personnel
leading to improper system operation and maintenance, and (2) design
deficiencies in the areas of system flexibility, system reliability and failure to
account for variables such as infiltration and inflow. These problems with
conventional treatment plants would be duplicated in wastewater aquaculture
projects, if not adequately addressed In the early stages of development.
As with any wastewater treatment facility, the successful implementation of
aquaculture treatment systems is highly dependent on proper design and
operation. However, due to the fact that there have been relatively few full
scale facilities from which actual field experience in use of aquaculture
wastewater treatment systems can be gained, and due also to lack of experience
and documentation of the ecological and biological complexity of these systems,
guidelines for optimal system design and operation are still in an early
developmental stage.
Lack of information about system design forces regulatory agencies and
engineers to apply safety factors which must be excessively large until data
becomes available to better optimize designs. This leads to an unfavorable
situation with regard to facility costs for construction and operation.
6-1
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Therefore, an identification of technical deficiencies and restraints on
wastewater uses for aquaculture was considered important to reveal research
needs that, when met, will allow more cost-effective designs.
This Chapter addresses design and operation considerations for wastewater
aquaculture facilities.
6.1 Design Considerations
Design of a successful aquaculture treatment system is based on a number of
design considerations which can be grouped into the following chronological
phases:
Process evaluation and selection of aquatic species
Treatment process train development
Treatment process design and process control
Cost-effectiveness analysis
Detail system design
Construction cost estimate
System operation, maintenance, and management
Construction inspection and management
6.1.1 Selection of Aquatic Species and Process Evaluation
Aquatic processing units (APU) can be used alone to treat raw wastewater
directly or as part of the process train in combination with more conventional
wastewater treatment processes. The selection of an APU including selection of
aquatic species is a complex task which should abide certain scientific and
engineering principles. Unlike conventional treatment systems, the criteria for
APU selection are not widely published nor as readily available for aquaculture
treatment systems, a factor which complicates the selection process.
Considerations in the selection of an APU may include:
Wastewater pretreatment and post-treatment requirements
Species naturally occurring and locally available
Adaptability of species to wastewater under investigation
Vulnerability or susceptibility of the species to climatic factors
Vulnerability or disease susceptibility of the species to wastewater
parameters (both conventional and priority pollutants)
Seasonal and annual productivity of the species
Site specific requirements
6-2
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The most favored candidate species for a contemplated aquaculture treatment
system are those which are most adaptable to the wastewater, tolerant to all
wastewater parameters without exotic pretreatment, productive on a year-round
basis, least constrained by site conditions, and require the least post-treatment
attention. Once the candidate species are selected, the type of APU (plant,
animal, combined, or wetland process) can be preliminarily determined.
Since most, if not all, of existing aquaculture treatment systems are
experimental it is believed that the selection of aquatic species has been largely
influenced by each researcher's knowledge about available species, species
characteristics and possibly even the funding potential for experimentation with
a particular species. The rationale behind the selection of species, in general,
has not been well-documented.
The history of aquaculture treatment technology development has been one
which evolved from using aquatic species for renovation of treated effluent to
eventual use of various species for treatment of raw sewage. Most species
tested to date have been used to treat municipal wastewater. The lack of
criteria with which to screen and select candidate species undoubtedly
contributes to limiting wider application of aquaculture treatment systems, as
compared to conventional treatment systems. A systematic approach to selecting
species is needed and is yet to be developed.
Also, review of the past history of wastewater aquaculture has indicated that
great emphasis has been placed on water hyacinths as potential aquatic species
for aquatic processing units. Due to severe geographical constraints (i.e.,
continual water hyacinth growth is very limited geographically to areas such as
southern Texas and Florida) and institutional constraints (i.e., water hyacinths
are considered a nuisance species whose import is prohibited by a number of
states), water hyacinths have very limited application for aquaculture treatment
systems. The most recent trends, as a result of more technical data being
made available, are toward use of rooted emergent aquatic plants including
reeds, bulrushes and rushes as the most suitable candidates for aquaculture
treatment systems. Additional studies are needed, especially in the central and
northern states, to confirm the widespread suitability of emergent plants for
wastewater aquaculture.
6-3
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In reviewing a wide variety of studies on the feasibility of various aquatic
species for aquaculture treatment systems it was noted that most studies were
conducted under controlled environmental conditions (e.g. a greenhouse) and on
a short-term basis. Although, many experiments provided encouraging results,
the performance of most aquatic species under low temperature conditions has
not been satisfactorily addressed nor have cost-effective mitigative measures
against the adverse effects of low temperatures been developed. Additionally,
aquaculture treatment technology researchers have tended to place study
emphasis on liquid treatment aspects and the solids disposal problems which
accompany various species are often neglected. Biomass removal, utilization,
and disposal aspects for various species should be addressed as part of species
selection.
6.1.2 Treatment Process Train Development
The term aquatic processing units (APU's) has been recently introduced by
Stowell, et al. The APU concept avails the potential for logical construction
of alternative aquaculture treatment process trains for a specific project.
The type of APU and species preliminarily selected dictates the treatment
process train. A process train defines the interrelationship between unit
process elements which are further developed in the treatment process design.
Basically, an aquaculture treatment process train should consist of the
following:
preliminary treatment processes compatible with the APU's
contemplated
appropriate number and types of APU's to achieve the level of
treatment required and to provide consistent treatment on a
year-round basis
compatible post-treatment processes to condition the treated effluent
with the objectives of meeting necessary discharge permit conditions
biomass harvesting, processing, and handling process
side liquid streams which have to be fed back to the main liquid
processing stream.
As indicated in Figure 6.1 an aquaculture treatment process train may, in
general, consist of pretreatment units, APU's, post-treatment units, effluent
6-4
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Figure 5.1
SIMPLIFIED FLOW DIAGRAM OF TYPICAL
AQUACULTURE TREATMENT SYSTEMS
Effluent Recirculation
i
Ul
1
1
1 1
\
Raw Sewage f ^ P re -Treatment
or Wastewater I Process Units
* /
1
1
' Side
1 Stream
| Returns
I
}
Sj.de Stream Returns
-—- i
/ Aquatic \ Post -Treatment | Diacharqe or
I Process Unitsy Process Units Reuse of
1 '
Harvesting and
Processing Units
V
Bidraass Utilization or Disposal
-------
disposal/utilization options, and solids processing and utilization methods. Each
of these unit processes must:
be compatible with unit processes upstream and downstream
be compatible with site conditions
provide environmental conditions conducive to the growth of the
aquatic species
produce effluent quality sufficient to meet discharge or reuse
standards
relieve environmental stresses so that the aquatic species do not
become disease-prone
have adequate environmental safe-guards against such problems as
odor', insect vectors, rodents, fire, and other public health and
safety considerations.
Although indicated in Figure 6.1 for a typical system, the question of
recirculation in APUs has not been resolved. The great majority of existing
(2 3)
APUs do not incorporate recirculation. Englande and Tridech ' were able to
demonstrate the benefit in APU performance and stability by effluent
(4)
recirculation. Vanhurizan tested the effluent recirculation concept using
water hyacinth ponds and found that effluent recirculation not only improved
effluent quality in terms of BOD and TSS, but also increased the capacity of
the treatment unit. Recirculation ratios of approximately 3 to 6 were used.
The effluent of the recirculation unit treating secondary effluent had an
average BOD of 15 mg/1 and TSS of 30 mg/1, as compared to a similar
once-through system producing average BOD of 58 and TSS of 69 mg/1.
Apparently, effluent recirculation is capable of maximizing process throughput.
However, the beneficial effect of effluent recirculation remains a technical
question awaiting further investigation in order to advance the APU concept,
especially when aquatic animals are used in treatment systems.
Once the treatment process train is developed, the water quality conditions
before and after each unit process can be defined. This information can then
be interpreted to produce the optimal arrangement of the unit components of the
process train. The treatment process train so developed forms the basis for
detailed process design and preliminary cost estimates. Unfortunately, very
limited literature is available in the area of aquaculture treatment process train
development and designers contemplating aquaculture treatment systems are
faced with technical difficulties in obtaining literature. This situation in itself
is a deterrent to application of aquaculture technology. In extreme cases,
6-6
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designers may need to conduct pilot studies in order to finalize a treatment
process train concept, and this too is a deterrent.
6.1.3 Treatment Process Design and Process Control
Once the treatment process trains are developed, each process element can be
determined. Treatment process design yields information, necessary for
preliminary system cost estimates and parameters essential in detail system
design. From available literature it is apparent that parameters affecting
aquaculture treatment process design are not well-understood. Most of the
available literature is rather localized and applicable to the specific localities
where the experimental or pilot systems were conducted.
Considerations necessary in developing the process design of an APU. have
been identified by a number of researchers and designers. They can be
grouped into the following categories:
pollutant loading rates to an APU
wastewater characteristics and pretreatment requirements
physical and chemical parameters
environmental parameters
biomass handling
process start-up and acclimatization requirements
Pollutant loading rates determine the physical dimensions, number of stages,
and redundant number of APUs and the flow distribution pattern in an APU.
Depending on the level of treatment to be achieved by an APU, the pollutant
loading rates to be considered should include:
localized and overall BOD loading rates
localized and overall TSS loading rates
localized and overall TKN loading rates
localized and overall loading rates of other pollutants
seasonal productivities of the aquatic species
tolerance levels of the aquatic species to various pollutants (e.g.,
phenol, heavy metals, etc.) to be removed by the APU
accumulation rate of phosphorus
accumulation rate of volatile and inert solids
6-7
-------
Certain physical and chemical parameters also affect some basic requirements of
an APU. The major considerations in terms of physical and chemical parameters
should include at minimum:
hydraulic loading rates, and maximum horizontal transport velocity to
prevent scouring or re-entainment of bottom sediments
control of flood and area-wide run-off
sludge storage volume required in an APU
temperature and auxiliary heat input requirements
diurnal dissolved oxygen level and aeration requirements
pH
diurnal alkalinity.
6.1.4 Available Design Criteria
Design criteria regarding process designs of aquaculture treatment systems have
been proposed and used by a number of researchers. Some of the criteria are
summarized in Table 6.1. It should be noted that these design criteria have
been applied to a limited number of systems. The geographical transferrability
of these design criteria to project sites other than those where the specific
research was conducted has not been evaluated and presents an area for
further investigation and research.
Most of the proposed design criteria or parameters tend to be related to
steady-state equilibrium conditions of aquaculture treatment systems. In fact,
most aquaculture treatment systems are greatly influenced by a number of
environmental factors such as temperature, (especially freezing), wind, soils,
local ecologic elements, and other climatic elements. Aquaculture treatment
systems however rarely perform under steady-state conditions, and are instead,
non-steady state and dynamic in nature.
Few published process design procedures attempt to account for the dynamic
variability of aquaculture treatment systems. In dynamic aquatic process units,
there are often rate-limiting reactions which collectively determine the overall
performance of an aquaculture treatment system. Methods by which the
reaction rates of these rate-limiting reactions can be controlled to maintain or
improve the performance level of an aquatic process unit are not
well-developed. Due to the lack of satisfactory solutions to these types of
technical problems, design of aquaculture treatment systems must by necessity
6-8
-------
Table 6.1
PROPOSED DESIGN CRITERIA FOR AQUACULTURE TREATMENT SYSTEMS
Type of
Treatment
Unit Water Surface
Area (acres/HGD)
water Depth (ft)
Detention Time (days)
BOD5 loading tlb/ac-day)
TSS loading Ub/ac-day)
TKN loading (Ib/ac-day)
Total f loading
(Ib/ac-day)
Individual Basin Area (ac)
length i Width Ratio
Width for Ease of
Harvest (ft)
Water Temperature (°F)
Dual or Multiple Systems
Mosquito Control
Initial Aeration
Solids Breakthrough
Velocity (ft/hr)
Productivity
(wet tons/ac-yr)
Harvest of Biomass
Harvest Frequency
and Criteria
Water Hyacinth Duckweed Heeds/BuJ rushes (Pope.et al)
(Stowll et al)
2° Treatment of 3° Treatment of
Raw Sewage 2° Effluent
Without Nutrient With Nutrient
Removal Removal
40-50 12
4-5 3-4
40-50 5-10
20-30 50-60
—
2.6-17.4
(avg. 13.4)
— 0.8-4.3
1-2 1-2
3il 3:1
25-30 25-30
50 68
Essential) 2-3 Essential] 1-3
Cells in Series Cells in Series
essential Essential
(use Gaabusia) (use Gaabusia)
Essential Essential
Not Reported Hot Reported
100-1,000 100-1,000
Essential Essential
Hot Reported Not Reported
(Wolverton)
2" Treatment of
Raw Sewage
First Second Overall
Basin Basin System
— — 28
S-8
36 21 57
84 20 54
86 78 55
—
_
__
—
— _ ^— ^m —
Warn Weather
Essential i 2
Cells In Series
Not Reported
Not Reported
Not Reported
300
Essential
Not Reported
2° Treatment of 3° Treatment of
Raw Sewage Raw sewage
needs Bulrush Overall needs Bulrush Overall
Trench Trench System Trench Trench System
4.1 4.1 8.2 4.1 4.1 8.2
4 2.5 — 4 2.5
0.5 2 2.5 0.5 2 2.5
380 180 190 36 23 IB
4OO 11O 200 38 20 19
80 60 40 30 20 15
46 32 23 29 25 15
„
6 12 — 6 12
12 12 12 12 12 12
Warn Heather Warn Weather
Essential) Multiple Cells Esi:ential(Multiple Cells
In Series S Parallel In Series s Parallel
Not Reported) Not Practical Not Reported). Not Practical
In Trenches In trenches
Hot Necessary Not Necessary
Not Reported Not Reported
700-66,000 7,000-66,000
Essential Essential
Not Reported Not Reported
3* Treatment of
2" Effluent
Henderson Dinges
26-36 6.2
3.9-4 2
35-47 5.3
6.5-7.B 27.1
8.7-23 47.4
1.6-2.3 9.4
0.7-2.6
—
—
^^
Warm warn
Weather Weather
Essential Essential ; 5
Cells in Scries
Not Reported
Essential, Especially in
Fish PoYids
Hot Reported 2.5-2.9 ft/hr
Essential
Function of Growth Rates
-------
Table 6.1 (cont'd)
Typ* of
Treatment
Prerequisite ICsnva,!
of Grot* Solids,
Oil/Gseaav
* Aquatic Plant Coverage
to Gupress M9«*
Sludge Btorage Volute
MquintBenta
Diurnal D.O. Problem
Diurnal Alkalinity
Problem
Effluent ^circulation
Hequlred
Threshold Toaicity of
Varioua pollutant (*)
to Sped**
Stocking Hequirement* for
Initial/Seasonal operation
Acclimation Period
Sludge nraoval
Requirements
Bloaaaa C.KiP Wtlo
Viomaae Hater Content
(» by Height)
Biomase Dewatering
Asqired
Attempted Biomass Disposal
or Utilisation mthoda
GnenhouH or Suppla*antal
Heat for Overwintering
Nitrogen Haaoval Ub/ee-yr
phoaphorua teakoval
(Ib/ac-yr)
nraoval of f» fr«ctory
Orqanlca and Trace Hetala
Mnoff Dlvenlon and Flood
Control ft quirt S
lUter Hyacinth
(Stow 11 at al)
2* Treatment ot 3* Treatment of
Maw Sewage
Without nutrient
Wanval
Tea
tMkaom
Yea
BOD Dependent
Mo
Unknown
Ui known
Hot Buggaatad
Hot Kuggaatad
Not Suggcated
100i6.S,1.4
9St
Tea
Uuidflll Coapost
FVrtillrer Soil
Conditioner
He thane
»aa
700
160
Ye», Date
Unknown
Yea
i* Effluent
Vith Nutrient
HaaKnral
yes
Unknown
Yea
Hot Sever*
TKJ! Dependent
(Jkiknown
Unknown
Hot Suggested
Hot Suggested
Hot Suggested
100,6.5,1.4
95*
Vea
Landfill Compost
Fertilizer Soil
Conditioner
Methane
Yea
700
160
Yes i Rate
Uh known
Yet
Duckweed
(Holvertcn)
2* Treata«nt of
Raw Sewage
rlrat Second Overall
Saaln B*ain Eystaa
yes
Unknown
tea
BOO Dependent
Ho
Uiknown
tkiknown
Hot Suggested
Hot Suggeated
Hot Suggeated
100tl2.8i2.2
95%
Yea
Landfill Compost
Fertiliser Soil
Conditioner
He thane
Vea
600
ISO
Yea( Bate
Uiknown
Tea
Mede/Bulruahes
2* tr«itaant of
taw Sewage
Deeds Bulruah Overal 1
Trench Trench System
Yes
unknown
Hot Deported
Uiknown i BOO
Dependent
Unknown
Uiknown
Unknown
Hot Kent toned
Hot Mentioned
Hot Mentioned
—
—
Tea
Landfill Compost
Fertilizer Soil
Conditioner
Methane
yea
300-700
300-700
yeai Mate
unknown
Te*
(Pope .at al)
3* Treataant of
Raw Sewage
Reeds Bulruah Overall
Trench Trench System
Yes
Uiknown
Mot Reported
Unknown i BOO
Dependent
"n known
unknown
Unknown
Mot Mentioned
Hot Mentioned
Hot Mentioned
••-
~
yea
Landfill Ooapost
fertilizer Soil
Conditioner
M0t K«n*
nei-nane
Yea
3 DO-TOO
300*700
Yeaj Date
Unknown
Yea
Polyculture
3* Ttaatawnt of
2* Effluent
Henderson Dingaa
Yea
Unknown-
Yea
BOO
Dependent
Unknown
Unknown
Unknown
Hot Suggeeted
Hot Suggested
Hot Suggeated
•-
—
—
Landfill Feed
Supplenent
rood
Yes
__
—
T**
-------
be conservative. This is a factor which is considered limiting to more
widespread application of the technology. This is especially true of natural
wetland-based treatment systems, for which the majority of the removal
mechanisms are either not well-understood or have not been quantified.
To address the dynamic nature of aquatic processing units for aquaculture
treatment system design, several analytical models have been suggested. Gee
and Jenson proposed the use of a BOD equation, and an equation for sizing
of a conventional treatment lagoon to determine the preliminary size of a water
hyacinth treatment system for both summer and winter conditions. An
adjustment is then applied to the preliminary sizes by considering the nutrient
removal rates of typical water hyacinth pond systems.
(31)
King examined the alkalinity requirements and limitations on aquaculture
treatment systems where the treatment objective was nutrient removal. King
indicated the diurnal dynamic nature of alkalinity in the water column which is
regulated by availability or shortage of inorganic carbon. Shortages of
inorganic carbon can have a great impact on aquatic plants. The three sources
of inorganic carbon available to photosynthetic aquatic organisms are:
respiratory carbon dioxide from heterotrophic aquatic organisms and
microorganisms, atmospheric recarbonation, and the carbonate-bicarbonate
alkalinity reservoir within an aquatic system. Of these three sources, the only
significant reserve of inorganic carbon is contained within the alkalinity which
supplies inorganic carbon to aquatic phytoplankton for photosynthesis in
enriched waters. Withdrawal of carbon dioxide by aquatic plants causes a
change of the system chemistry, most of which favors physical-chemical removal
of phosphorus, metals, and depending on the form present, nitrogen.
During daylight hours, aquatic plants withdraw the free carbon dioxide from
the water at a rate greater than can be replenished by atmospheric
recarbonation and respiratory sources, causing a net depletion of bicarbonate
and hydrogen ion concentrations and an increase in pH. This increase in pH
results in formation of calcium carbonate precipitates which trigger some
physical-chemical removal mechanisms and favor removal of phosphorus, ammonia
and heavy metals. Ammonia can become partially volatilized due to the high pH
environment. At night, the process is reversed. With this hypothesis, King
6-11
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suggested the following analytical equation for calculating nitrogen removal
ra,e:(31)
N, = N0C-°-03t
Where:
N. = total nitrogen concentration (mg/1) at time t.
N = initial total nitrogen concentration (mg/1) at time zero.
t = time (days)
The kinetic nitrogen removal coefficient (0.03) is dependent on water
temperature and the aquatic species used. King was able to demonstrate that
nitrogen removal by an aquaculture treatment system was predominated by
volatilization of ammonia, nitrification and denitrification by microbial
chemotropic reactions, and to a lesser degree by plant uptake. Whether this
hypothesis is valid requires in-situ and real time monitoring results of carefully
designed experimental systems.
King also indicated that removal of phosphorus is affected by dynamic pH
variations, and suggested that total phosphorus concentrations exceeding 40
mg/1 might be toxic to water hyacinths. Whether long-term operation of an
aquaculture treatment system will result in the pooling of phosphorus in the
bottom sediments to a saturation level beyond which significant removal of
phosphorus is eliminated and break through of phosphorus ensues is a
debatable issue. The same concern may be raised for nitrogen removal in an
overloaded aquaculture treatment system.
(2 3)
As discussed in Chapter 2, Englande and Tridech ' were able to demonstrate
that the removal kinetics of various aquaculture treatment systems for various
pollutants (including BOD, boron, arsenic, and heavy metals) follow certain
mathematical models including a first order kinetic model and a composite
exponential kinetic model. In addition, the uptake kinetics follows closely a one
compartment model or a two-compartment model. Unfortunately, these
6-12
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experiments were conducted under favorable temperature conditions in a
greenhouse. How these kinetic coefficients vary with water temperature remains
undefined and requires further research.
In order to make aquaculture treatment systems acceptable, they must be
designed with adequate considerations to public health and environmental
protection. Among the environmental considerations are:
control of disease vectors (e.g., insects especially mosquitos,
rodents, birds, etc.)
control of odor
protection of health and safety of operators
control of runoff from entering the treatment system
protection of the system from flood damages
protection of groundwater resources from contamination by the
treatment system as a result of infiltration and short-circuiting of
wastewater to the groundwater systems
control of erosion by avoiding excessive slopes and bare ground
surface
control of freezing problems, when necessary
control of plant growth to minimize the potential of becoming an
environmental nuisance (such as clogging of waterways by spreading
of water hyacinth).
Mitigative measures to avoid adverse environmental effects have been casually
(32)
suggested in the literature. In fact, mitigative measures, in most cases,
are site specific and should be developed and evaluated locally for the
aquaculture treatment processes contemplated. It is suggested however, that
certain minimum guidelines should be made available to guide and assist
environmental planners and designers of aquaculture treatment systems.
The processing and handling of biomass produced by an aquaculture treatment
system is an integral part of the system and should be designed in a manner
that is compatible with other portions of the system. Depending on the
treatment goal, harvesting of biomass from aquaculture treatment systems can
be essential to maintaining optimal treatment efficiency and optimal growth of
6-13
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aquatic species in the system. Unfortunately, most of the available literature
fails to draw conclusions regarding the amount of harvest in each harvesting
period, the frequency of harvest, time of harvest, and method of harvesting.
Additional criteria for determining harvest volume, frequency and method needs
to be developed.
Aquatic species, especially aquatic plants, contain tremendous amounts of water.
In order to render the biomass suitable for beneficial uses, it must be
dewatered and sometimes dried. The most economic means of biomass
dewatering and drying are still in a developmental stage. Additional discussion
of biomass processing is presented in Chapter 8.
In order to have a successful aquaculture treatment system, the design must
provide adequate features in the system to facilitate process system start-up.
During the initial or seasonal start-up of a system, design features must be
provided for transplanting or stocking the aquatic species, acclimating the
species (whether juvenile or adult) to the waste water to be treated, and
promoting the growth at various growth stages for optimal utilization of the
system. Various design features should be provided to ensure a consistent
level of treatment of the wastewater when components are being repaired or
during initial or seasonal system start-ups. Literature regarding system
acclimatization and start-up is extremely limited. This presents a major
constraint on the wider application of aquaculture treatment technology.
In addition, what elements are essential in terms of process quality monitoring;
and what feedback mechanisms should be made .available to allow future design
and operational changes to maintain quality assurance and quality control are
some of the technical questions for which answers should be incorporated into
the process design. Among the technical questions which remain to be
answered are:
For process control, is simply sampling system influent and effluent
adequate?
What additional monitoring points and parameters are needed in order
to assure consistent high level of performance?
6-14
-------
If a system is designed to remove phosphorus, is it necessary to
sample and monitor phosphorus content of bottom sediments and water
columns in an APU?
Is it necessary to monitor sludge blanket level in an APU, and what
is the frequency desirable?
Is groundwater quality monitoring necessary and how extensive should
the system be to detect any degradation of groundwater resources?
Is an odor detection system necessary and how extensive should the
system be?
What are the minimum and optimal environmental monitoring systems
and control measures to be incorporated into the design of an APU to
minimize odor, disease, mosquito, and other potential environmental
nuisance problems?
6.1.5 Cost-Effectiveness Analysis
Prior to adoption of an aquaculture treatment system, a cost-effectiveness
analysis including all costs and environmental considerations should be
performed. Comparable conventional treatment alternatives should be analyzed
along with prominent aquaculture treatment alternatives in the cost-effectiveness
analysis. Preparation of a thorough cost-effectiveness analysis would definitely
enhance the implementability (i.e., public acceptance) of a contemplated APU
system where such a system is demonstrated cost-effective.
Cost-effectiveness analysis procedures for aquaculture treatment systems are
essentially the same as those used for conventional treatment systems.
However, unlike conventional systems, some of the cost items (e.g., costs for
transplanting species, acclimating species, harvesting, etc.) have not been well
documented. Judgemental pricing decisions are necessary at this stage in the
development of aquaculture treatment technologies and difficulties encountered
in assigning a monetary value to specific APU components may become a
significant deterrent to final implementability. Adequate disclosure and
assessment of these items in qualitative rather than monetary terms would help
the implementation of an APU system. However, procedures, approaches, or
methodologies for assessing these intangible items are simply not available and
require additional investigation. These non-monetary items may include but are
not necessarily be limited to:
6-15
-------
Compatibility of an APU system with the candidate sites and their
surrounding land uses.
Environmental issues (odor, diseases, food chain control, public
health and safety, etc.)
Long-term and short-term reliability of APU systems especially in the
areas of long-term local ecological changes resulting from
implementation of APU systems.
Additional discussion of the cost-effectiveness aspects of APU systems is
provided in Chapter 7.
6.1.6 Detail System Design
The most critical design problems should be addressed completely in the process
design of an APU. Detailed system design is simply a translation of all process
design computations into physical or structural requirements. These
requirements fall under several groups:
hydraulic requirements
mechanical requirements
electrical requirements
instrumentation and laboratory requirements
structural requirements
site requirements
Detailed system design should conform to the concepts established in the
process design phase of an APU system. The spatial, hydraulic, and other
physical arrangements determined in detailed system design simply fulfill all of
the requirements identified and quantified in the process design phase with an
adequate margin of safety.
Detailed system design is relatively an easier task compared to process design
of an APU. For low-technology systems, specifications for electrical,
mechanical, and structural engineering items should be available. Site plans for
aquaculture treatment systems can be developed based on available site planning
procedures and codes applicable in the application area, except for natural
wetland treatment systems, for which site planning elements have not been
delineated and require further research efforts.
6.1.7 Construction Cost Estimates
Once the detail system designs are completed, construction cost estimates can
be prepared based on local prevailing labor and material rates, and quotations
6-16
-------
from equipment manufacturers. The only area of weakness in construction cost
estimates may be the costs of biomass harvesting equipment. Additional
investigation efforts may be needed in this area to enable designers to obtain a
more accurate cost estimate.
6.1.8 System Operation, Maintenance, and Management
There is a very limited knowledge and recorded experience in operation and
maintenance (O & M) of aquaculture treatment systems due to the newness of
the concept. In general, an appropriate O & M system of an aquaculture
treatment system should include the following elements:
A comprehensive O & M manual
A proper management organization of personnel with necessary trades
and skills in managing aquaculture treatment technology
An O & M manual should address the following aspects of an aquaculture
treatment system:
1. Purpose and objectives of the aquaculture treatment system
2. Detailed description of all unit processes, their capabilities and
limitations
3. Detailed description of all equipment, and instruments; and their
intended uses, capabilities and limitations
4. The relationship between unit processes
5. Procedures for starting-up the system and its components
6. Emergency procedures to minimize system upsets and overloading
7. Sampling procedures and process monitoring requirements
8. Routine procedures for operating the system including harvesting
schedules
9. Maintenance items and scheduling
10. Trouble-shooting guide for identifying and correcting process or
equipment problems.
The O & M of aquaculture treatment systems is characteristically different from
that of conventional treatment systems. Lack of experienced personnel for
operating APU systems dictates explicit O & M instructions to ensure proper O
6-17
-------
& M of the systems. Because the majority of existing and past non-operating
aquaculture treatment systems are either experimental in nature or at the
pilot-study stage, there is a significant lack of O & M procedures. This is an
area which dictates further investigation and research. Better record keeping
and dissemination of O & M related data and information is needed to facilitate
wider application of aquaculture treatment technologies.
6.1.9 Construction Inspection and Management
In order to maintain aquaculture treatment systems as low-energy, and
inexpensive technology alternatives, proper construction supervision and
inspection are essential. While too vigorous construction supervision and
inspection can increase the cost of aquaculture treatment systems beyond the
cost-effective domain. Lack of proper construction supervision and inspection
may result in defective systems or systems incapable of performing according to
the design and design goals. The best approach to construction supervision,
inspection, and management remains to be addressed.
6.2 Summary
Over the last decade much has been learned about design of aquaculture
treatment systems. Nevertheless, wider application of the technology and wider
acceptance by engineers, regulatory officials, and the public still greatly
constrained by various weaknesses in existing technical documentation. These
technical constraints to aquaculture technology implementation can be decreased
through further documentation with regard to the following:
Proper procedures for screening, selecting, and adopting candidate aquatic
species for the aquaculture treatment project contemplated.
Better understanding and even quantification of removal mechanisms which
occur in an aquaculture treatment system.
Effects of environmental or climatic factors on these removal mechanisms.
The threshold concentrations of various pollutants tolerable by various
aquatic species.
The optimal environmental conditions for growing various aquatic species
and cost-effective techniques for achieving and maintaining these
conditions.
6-18
-------
Better understanding of various wastewaters and levels of pretreatment
requirements prior to discharge into an aquatic processing unit (APU).
Better documented procedures for starting-up, operating, and maintaining
an APU and better understanding of APU controllability and strategies for
process control.
Better understanding of the role of biomass harvesting (criteria, timing,
and frequency) in an aquaculture treatment system.
Ability to obtain accurate predictive mathematical models for various APUs
by considering dynamic and kinetic nature of APUs.
6-19
-------
REFERENCES
1. Stowell, R. R. Ludwig, J. Colt and G. Tchobanoglous, "Toward the
Rational Design of Aquatic Treatment Systems", Department of Civil
Engineering, University of California, Davis, California, 1980.
2. Englande, A.J., Jr., and B. Kaigate, "Removal of Persistant Heavy Metals
by Vascular Aquatic Plant Systems", Paper Presented at 1981 Annual
Meeting of American Institute of Chemical Engineers, New Orleans,
Louisiana, November 8-12, 1981.
3. Tridech, S., Trace Contaminant Removal from Secondary Domestic Effluent
by Vascular Aquatic Plants, Ph.D. Dissertation, Tulane University,
March, 1980.
4. Vanhurizan, and S. Wilson, "Solar Powered Wastewater Treatment Plant",
prepared for the City of San Marcos, San Marcos, Texas, November
6, 1981.
5. Dinges, R., "Development of Hyacinth Wastewater Treatment Systems in
Texas", Seminar Proceedings and Engineering Assessment
Aquaculture Systems for Wastewater Treatment, EPA Publication,
430/9-80-006, Washington, D.C., Sept. 1980 (pp. 193-226).
6. Dinges, W.R., "Upgrading Stabilization Pond Effluent by Water Hyacinth
Culture", Journal of the Water Pollution Control Federation, Vol. 50,
No. 5, pp. 833-845, May 1978.
7. Steward, K.K, "Nutrient Removal Potentials of Various Aquatic Plants",
Hyacinth Control Journal, 8_, 34 (1970).
8. Wolverton, B.C. and R.C. McDonald, "Upgrading Facultative Wastewater
Lagoons with Vascular Aquatic Plants", Jour. WPCF, Feb. 1979 (pp.
305-313).
9. Stowell, R., R. Ludwig, J. Colt, and G. Tchobanoglaus, Toward the
Rational Design of Aquatic Treatment Systems, Department of Civil
Engineering, University oTCalifornia, DavisT, California, August,
1980.
10. Wolverton, B.C., et al, "Water Hyacinths and Alligator Weeds for Final
Filtration of Sewage", NASA Technical Memorandum No. TM-X-72724,
1975.
11. Harvey, R.M and J.L. Fox, "Nutrient Removal Using Lemna minor", Jour.
WPCF, Vol. 45, pp. 1928-1938, September 1979.
12. Pope, P.R., "Wastewater Treatment by Rooted Aquatic Plants in Sand and
Gravel Trenches", EPA Technical Report, Grant No. R-805279,
February 1981.
6-20
-------
13. Seidel, K., "Macrophytes and Water Purification", Biological Control of
Water Pollution, J. Tourbier and R.W. Pierson, Jr., Eds., University
of Pennsylvania, Philadelphia, Pennsylvania, pp. 109-121.
14. Boyt, F.L., S.E. Bayley and J. Zoltek, Jr., "Removal of Nutrients from
Treated Municipal Wastewater by Wetland Vegetation", Jour. WPCF,
May 1977 (pp. 789-799).
15. Tchobanoglous, G., and G.L. Gulp, "Wetland Systems for Wastewater
Treatment: An Engineering Assessment", Paper presented at a
seminar on Aquatic Systems for Wastewater Treatment, University of
California, Davis, California, September, 1979 (pp. 13-42).
16. Mann, R. and Ryther, J.H., "Trace Contaminant Accumulation by
Organisms Grown in A Waste Recycling Aquaculture System", Proc.
World Maricul. Soc. 10, 1979 (pp. 809-822).
17. Mann, R. and Ryther, J.H., "Growth of Six Species of Bivalve Molluscs in
a Waste Recycling-Aquaculture System", Jour. Aquaculture, Vol. 11,
1977 (pp. 231-245).
18. Ryther, J.H., L.D. Williams and B.C. Kneale, "A Fresh Waste Waste
Recycling-Aquaculture System", Jour. Florida Scientist, Vol. 40, 1977
(pp. 130-135).
19. Burks, S.L. and J.E. Matthews, "Effectiveness and Cost of Activated
Carbon Adsorption of Toxic Compounds from Petroleum Refinery
Wastewater", Project Summary.
20. Vance, D., "Effluent-Raised Salmon Head Out to Sea", The Lumberjack,
Vol. 54, No. 27, May 1979 (pp. 21).
21. Aim, A., "Wastewater Alternative Promising for Fish, Finances", Vol. 55,
No. 1, Sept. 1977 (pp. 16).
22. Avault, J.W., "Water Temperature", Aquaculture Magazine, Vol. 6, No. 4,
1980 (pp. 41).
23. Behrends, L.L., "Recycling Livestock Wastes Via Fish Culture",
Aquaculture Magazine, Vol. 7, No. 1, 1980 (pp. 38-39).
24. Henderson, S., "Utilization of Silver and Bighead Carp for Water Quality
Improvement", Aquaculture Systems for Wastewater Treatment:
Seminar Proceedings and Engineering Assessment, EPA Publication No.
430/9-80-006, Sept. 1979 (pp. 309-349).
25. Stanley, R.A., "Methods of Biological Recycling of Nutrients from
Livestock Waste" A Literature Review and Systems Analysis",
Tennessee Valley Authority, Muscle Shoals, Alabama, August 1974.
26. Allen, G.H. and Hepher, "Recycling of Wastes Through Aquaculture and
Constraints to Wider Application", FAO Technical Conference on
Aquaculture, Kyoto, Japan, May 26-June 2, 1976.
6-21
-------
27. Bahr, T.G. and D.L. King, "Municipal Wastewater Recycling: Production
of Algae and Macrophytes for Animal Food and Other Uses",
Development in Industrial Microbiology, Vol. 18, 1977 The Siciety for
Industrial Microbiology, (pp. 121-134).
28. Dinges, R., "A Proposed Integrated Biological Wastewater Treatment
System", in Biological Control of Water Pollution, J. Tourbier and
R.W. Pierson, Jr., editors, University of Pennsylvania, Pennsylvania,
pp. 225-230, 1976.
29. Henderson, S., "An Evaluation of Filter Feeding Fishes for Removing
Excessive Nutrients and Algae from Wastewater", Project Report to
U.S. EPA, Robert S. Kerr Environmental Research Laboratory, Ada,
Oklahoma.
30. Gee & Jenson, "Water Hyacinth Wastewater Treatment Design Manual",
prepared for NASA/National Space Technology Laboratories, NSTL
Station, Mississippi, June 1980.
31. King, D.L. and T.G. Bahr "Wastewater Recycling: Coupling Aquatic and
Land Irrigation Systems", Proceedings of Specialty Conference on
Environmental Aspects of Irrigation and Drainage, American Society of
Civil Engineers, New York, 1976 (pp. 128-137).
32. Yount, J.L. and Grossman, R.A., Jr., "Eutrophication Control by Plant
Harvesting", J. WPCF, Vol. 42, No. 5, Part 2, May 1970 (pp.
R173-R183).
6-22
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Chapter 7
ECONOMICS OF WASTEWATER AQUACULTURE
COMPARED TO CONVENTIONAL TREATMENT TECHNOLOGIES
7.0 INTRODUCTION
As has been mentioned, dramatic increases over the last decade in the
construction and operating costs of wastewater treatment facilities provide an
incentive to seek and apply technologies which keep such costs as low as
possible. The one factor which has caused perhaps the greatest increase in
operating costs is the use of electrical and fuel energy. Wastewater
aquaculture treatment, with its dependence on naturally occurring rather than
chemically or mechanically induced pollutant removal can be considered a
low-energy technology. Hence, where implementable, aquaculture has the
potential for lower operating costs compared to more conventional mechanized
technologies while providing tertiary and advanced levels of treatment. As
indicated in Table 7.1, the more natural systems such as land treatment and
aquaculture have a clear advantage over more mechanized systems on the basis
of total annual energy consumption and comparative level of performance.
(2)
Tchobanoglous, et al concluded that both land treatment systems and
aquaculture treatment systems can offer substantial savings in energy and the
amount of resources consumed compared to conventional wastewater treatment
systems. Crites also demonstrated that aquaculture can provide a low cost, low
(4)
energy solution for wastewater treatment. Preliminary calculations by Lee
and McKim based on the aquaculture treatment systems at Walt Disney World
indicated that the wastewater hyacinth treatment system utilizes only 50 percent
of the energy of a comparable activated sludge system for secondary
treatment. A separate comparison between total energy use for equivalent
performance between an activated sludge process and a constructed wetland
process preceded by a facultative pond showed that the energy difference
7-1
-------
Table 7.1
TOTAL ANNUAL ENERGY FOR TYPICAL 1 MGD SYSTEM
(ELECTRICAL PLUS FUEL, EXPRESSED AS 1000 KWH/YR)
tsj
Treatment system
Rapid infiltration (facultative pond)
Slow rate, ridge 4 furrow (fac. pond)
Overland flow (facultative pond)
Facultative pond 4 interm. filter
Facultative pond 4 microscreens
Aerated pond 4 interm. filter
Extended aeration 4 sludge drying
Extended aeration 4 interm. filter
Trickling filter 4 anaerobic digestion
RBC 4 anaerobic digestion
Trickling filter 4 gravity filtration
Trickling filter 4 N removal 4 filter
Activated sludge 4 anaerobic digestion
Activated sludge 4 an. dig. 4 filter
Activated sludge 4 nitrification 4 filter
Activated sludge 4 sludge incineration
Activated sludge 4 AWT
Physical chemical advanced secondary
Effluent quality
BOD
5
1
5
15
30
15
20
15
30
30
20
20
20
15
15
20
<10
30
SS
1
1
5
15
30
15
20
15
30
30
10
10
20
10
10
20
5
10
P
2
0.1
5
-
-
-
-
-
-
-
-
-
-
-
-
-
<1
1
N
10
3
3
10
15
20
-
-
-
-
-
5
-
_
-
-
<1
—
Energy
1000
kwh/yr
150
181
226
241
281
506
683
708
783
794
805
838
889
911
1,051
1,440
3,809
4,464
Source: (1)
-------
between the two processes (activated sludge is higher) increases with
/ C \
increasing flow volume (at least up to 1.0 MGD). Fritz and Helle indicated
that the cost of land, length of required force mains, flow, the type of cypress
wetland and surroundings are important variables which can have a significant
impact on the cost-effectiveness of cypress wetlands aquaculture treatment
(7)
systems. Further comparisons of land requirements, costs and energy usage
for aquaculture and more conventional technologies are summarized in Table 7.2
This study had originally intended to present a variety of case studies of the
economics of existing aquaculture facilities. The case studies were to be
selected to give a wide representation of geographic location, climatological and
hydrogeological characteristics, aquaculture species used, flow volumes, etc.
and were to be used for an economic comparison with conventional technologies
providing a similar level of treatment performance. As has been noted by other
researchers, one of the great difficulties in examining the economics of
wastewater aquaculture is the lack of verified design and operating data. In
reviewing various operating aquaculture facilities in the course of this study
several problems which contribute to the validity of an economic analysis were
noted.
For many of the aquaculture facilities, the advantage of the aquaculture
technology could not be compared quantitatively to conditions which existed
prior to aquaculture implementation. In other cases aquaculture facilities have
been retrofitted and design or construction quality may not be comparable to a
newly designed system. For example, the water hyacinth pond at the Hornsby
Bend sludge plant in Austin, Texas ranges from a few inches in depth near the
inlet to more than eight feet at the outlet, and is subject to short circuiting
due to its physical characteristics. Better performance would be expected if
such problems could be remedied, and it would be unfair to compare this system
to an ideal conventional treatment system without such problems.
The majority of aquaculture systems were, or are, research projects, which
typically have different cost associated witfy them than do non-research
wastewater treatment systems. For example, construction, operating and
monitoring is often provided by students and such situations are not comparable
to facilities which have been designed, bid, constructed and operated like
7-3
-------
Table 7.2
EXAMPLES OF TYPICAL LAND REQUIREMENTS, TOTAL CONSTRUCTION COSTS,
LABOR REQUIREMENTS, PARTS & SUPPLY COSTS, AND TOTAL ENERGY REQUIREMENTS
FOR NATURAL TREATMENT SYSTEMS, ACTIVATED SLUDGE
AND TRICKLING FILTER SYSTEMS
Treatment
Land rxq'd, acres
Plant nice, »fd
0.1 0.5 1.0
Total Const. Coil
n«nl size,
0.1 0.5
? *X10*6
nfd
1.0
Labor rtq'd, p
flant slfcn
0.1 0.5
•h/yr
, «C4
1.0
Conventional Systems
Activated
High Hate
Slirir.e + 01
(fir.) rrtckllM
1.0
1.5
2.5
3.0
i».0
5.0
0.710
0.732
\.zyt
1.276
1
1
.600
.700
1600
1200
3C.OO
2''00
5500
!»200
FilUnr + 01
Land fret
IVlMry *
FVlMry *
rrlaary *
rrlmry *
Fflc. rood
Fac. Pond
Fao. IV»it4
Fac. Hind
Ovarland Flow 4 Cl~
Rapid Infiltration
Slow Rate (SB)
Slow Rate (r * f)
* Over, Flow
« ftipld Infl.
* Slow Rate (««)
+ Slow Rate (r»f)
6.5
2.5
16.5
16.5
11.0
7.0
21.0
21.0
30.8
10.8
80.8
60. 8
1*5.0
25-0
95.0
95.0
61.5
21.5
161.5
161.5
90.0
50.0
163.0
163.0
O.'iOl
0.311
O.'»81
O.bzl
0.530
O.Ąrt
0.610
0.550
0.662
O.U72?
0.902
0.712
1.225
1.035
1 .1*5
1.275
1
0
1
1
1
1
2
2
.050
.790
.500
.130
.950
.690
.'100
.030
ir-oo
1500
2000
2000
2000
2WO
2VO
2500
3150
2950
3150
3150
WlOO
l»?00
ViOO
WiOO
«I200
'1000
«I200
«»200
5700
5500
5700
5700
Aquatic Treatment Systems
IVlMry +
Primary *
Fao. Food
Fur. Pond
Artlf. Wetland + Cl~
Water Hynclnthn + Cl"
+ Artlf. Ifetlnnd
+ Hater Hyacinths
0.5
2.5
9.0
7.0
20.8
10. fl
35.0
25.0
ftl.5
21.5
70.0
50.0
0.341
0.331
O.ii90
O.'l60
0.552
O.S22
1.115
1.005
0
0
1
1
.900
.'"TO
.*00
.730
1000
2000
1500
2500
2250
2750
3500
liOOO
3000
4000
itym
5500
Mi-la * S-jpfiHtn, J/jr x IO
P.nnl clzc, «r
0.1 O.S 1.0
~Z
Total Enemy
llnnt sit", mr-l
0.1 0.5 1.0
80
60
65
55
65
65
90
RO
90
90
35
35
60
60
120
100
95
90
95
95
135
130
135
135
*5
55
P5
95
160
I'm
130
120
130
130
IPO
170
1FO
teo
•50
PO
110
130
1872
16»H
1112
953
132*
?y>
1??3
I IP'".
nos
11V
1W.T
ir-?o
11 III
1132
5033 7ieo
3'-59 fX>»»i
22V, 3705
IP0* JW
•)iy> «'m5
?12i7n
?;PS «;?n
?OM 3320
?py yc°
2309 3°5P
215* 3<|52
2-'l75 3?2l
rftf
* Adapted fron Cchobanoglous, *t al., 1979
land cent not Included
? p'\\/yt • pemon tiours per year
Include-, both prlaary enersy (electricity and fuel) end secondary enersy (plant
" aoauenn influent to all syoteas In doaestlc wastewater with BOUc 4 S3 « 220 nc/1
' effluent expectud to achieve BODj * SS - 30 ns/1
Jj effluent expected to aclnlve 8(^)5 k SS = 10 »«/l, nurtlent removal «H1 v»rv with mijHp of operation
offlimnl npncted to achieve BODj * SS » 30 «g/l. ntirtlent rewo«-«l ulll *trr with mode Of "
" solid trt irrlnitlon systra
rld«)p t furrow Irrtijatlon systna
construction, ctaalcals. parts *
auppllss, etc.)
Source: (3)
-------
non-research facilities. Additionally, certain regulatory requirements for
components such as liners and coverings may have been relaxed for research
projects. Additional or special equipment may also have been provided for
research projects which might otherwise not be used in a conventional project.
For example, the hyacinth basins at the Walt Disney World research facility
were constructed with concrete and provided with additional piping and valving
for varying the operating modes for research purposes.
Wastewater aquaculture facilities in general are land-intensive, but in the
majority of aquaculture facilities surveyed, the required land was already
available at no additional cost. This situation would tend to give an unfair cost
comparison with conventional processes which are less land intensive. For
example, the Coral Springs aquaculture facility was constructed on available
land with no additional cost for the land. Since land in this area assumedly
has a high cost due to its prime location, aquaculture technology may not have
been cost-effective if the land had been purchased.
Finally, cost information for privately financed industrial aquaculture facilities
could not be obtained due to a perceived reluctance to share such information
with competitors.
7.1 Case Studies
Due to the limited amount of meaningful economic data on existing aquaculture
facilities for the reasons listed above, it was not possible to present ten
existing case studies, nor to use selection criteria based on location, flow, etc.
as originally desired. Eight total case studies, four based on existing
aquaculture facilities, three that deal with planned future aquaculture facilities,
and one hypothetical case study have been presented to provide further insight
into the economics of various aquaculture facilities.
Where appropriate, conventional processes capable of achieving effluent qualities
similar to aquaculture processes were compared with the existing facilities.
Cost data for the comparable conventional processes was derived from the U.S.
(8)
EPA Innovative and Alternative Technology Assessment Manual or from best
engineering judgement when data was not available. Economic comparisons were
7-5
-------
based on an evaluation of present worth for the first year of the system
f9)
operation in accordance with EPA cost-effectiveness analysis guidelines.
A hypothetical situation case study based on critical, fixed, site-specific
conditions and regulatory guidelines is presented to incorporate certain factors,
such as land costs, which were not included in the other case studies offered.
Because land requirements are usually greater for aquaculture technology, it
was felt that a case study comparing alternatives with land cost included must
be presented to show the effect of land purchase on cost-effectiveness. Design
and cost estimates for the hypothetical case study were generated as if for a
Step 1 Sewerage Facilities Plan. The hypothetical case involves the upgrading
of effluent from a stabilization pond located in Texas. The State of Texas is
the only state with design guidelines for aquaculture technology.
The following case studies will be presented:
National Space Technological laboratories, Bay St. Louis MS (existing)
Houghton Lake, MI (existing)
Coral Springs, FL (existing)
Lake Helen, FL (existing)
Gilbert, AZ (future)
Shreveport, LA (future)
Austin, TX (future)
Hypothetical Case Study, Texas
Tables 7.3 through 7.9 present summary descriptions and the findings of all
but the hypothetical case. A comment is included for each case to summarize
economic findings of the cost comparisons.
7.1.1 Hypothetical Case Study
For the hypothetical situation it has been assumed that the State of Texas is
requiring a POTW to be upgraded in terms of suspended solids removal. A
suspended solids limit of 30 mg/1 has been proposed. The existing system,
designed under Texas Department of Health Guidelines consists of a 5.6
acre facultative pond receiving raw wastewater, followed by a 5.6 acre initial
stabilization pond and a 6.3 acre final stabilization pond. A 100 foot fenced
buffer area surrounds the facility.
7-6
-------
Table 7.3
COST COMPARISON BETWEEN AQUACULTURE AND
CONVENTIONAL TREATMENT ALTERNATIVE
Case Study No. 1
Location: National Space Technology Laboratories - Bay St. Louis, Mississippi
Description: Upgrade existing 2 ha, (4.9 ac.) domestic wastewater lagoon No. 1 to meet effluent suspended solids
limitation.
Operating Conditions
Average Flow j 475 m3/d (0.125 mgd)
Surface Area : 2.0 ha (4.9 ac.)
Average Depth : 1.2 M (4.0 ft.)
Detention Times 54 days
Loading : 26 kg/ha-day (23.1 Ibs/ac-day)
Mean Effluent Quality
BOD5
TSS
Be fore
17
49
(mg/1)
After
5
10
Permit
30
30
Facilities Requirement .
Aquaculture
Add hyacinths to existing lagoon to reduce
suspended solids
Conventional Alternative
Dual media filter
Cost Item *
Capital Cost
O, M fi R Cost
Revenues
Present Worth
* 1976 Cost; i = 6-1/8%; Salvage = 0
Aquaculture ( $)
1,200
960
0
12,100
Conventional Alternative (S)
80,000
6,800
0
157,500
Comment: Addition of water hyacinths to lagoon upgraded performance to more than satisfy effluent requirement.
Capital costs were minimal due to existing lagoon. Harvesting costs have been minimal. Aquaculture
was significantly more cost effective due to low capital cost and energy usage. Note that hyacinth
facility is limited to warm climate area.
References; (8, 11, 12, 13)
-------
Table 7.4
COST COMPARISON BETWEEN AQUACULTURE AND
CONVENTIONAL TKEATMENT ALTERNATIVE
Cast Study No. 2
Location:
Houghton Lake Sewer Authority Wastewater Treatment Plant - Houghton Lake, Michigan
Description: Upgrade existing aerated lagoon effluent by pumping to natural wetland to meet suspended solids and
total phosphorous limitation (domestic wastewater)
Operating Conditions
Seasonal Wetland Discharge: 3785 m3/d-5678 K^
(1.0 MGD-1.5 MGD)
-4
oo
Mean Effluent Quality (mg/1)
TSS
TP
BeforeA After Permit
18 — B 10
4 .5 .5C
A - Estimated
B - Not determined because of detritus
C - Total dissolved phosphorus
Facilities Requirement:
Aquaculture
Holding pond modification
Dechlorination Pond
Pond wetland transmission
Irrigation header system
Monitoring equipment
Cost Item*
Capital Cost
O, M & R Cost
Revenues
Present Worth
* 1978 cost; i = 6-5/8%; sal^
Conventional Alternative
Chemical feed unit
Dual media filtration
Aquaculture ($)
400,000
36,000
0
794,200
•age = 0
Conventional Alternative ($]
543,000
68,500
0
1-;293,075
Comment: An example of a natural system is an area subject to sub-freezing winter weather. The most notable cost
difference between these two technologies is the 0, M, and R cost due to more labor, energy and chemicals
for the conventional alternative. The facility meets effluent discharge limits and no significant advers
environmental impacts have been reported. The aquaculture technology is cost effective.
-------
-J
10
Location:
Description:
Table 7.5
COST COMPARISON BETWEEN AQUACULTURE
AND CONVENTIONAL TECHNOLOGY
Case Study No. 3
Coral Springs Improvement District Wastewater Treatment Plant - Coral Springs, Florida
Upgrade existing activated sludge process effluent by hyacinth system to advanced wastewater
standards (domestic wastewater)
Operating Conditions
Average Flow : 378.5 m3/d (.1 MGD)
Total Surface Area: 0.5 ha (1.25 ac)
Detention Time : 6.0 days
Water Depth : 0.38 m (1.25 ft)
Facilities Requirement;.
Mean Effluent Quality (mg/1)
BOD5
TSS
TN
TP
BeforeA
20
25
9
8
AfterA
5
3
1-2.5
8
Permit
5
5
3
1
A - Estimated
Aquaculture
Five hyacinth culture
ponds in series
Cost Item*
Capital Cost
0, M, & R Cost
Revenues
Present Worth
* 1978 cost; i = 6-5/8%; salvage =
Conventional Alternative
Nitrification (seperate stage) process
Denitrifi cation (fine media) process
Dual media filtration
Aquaculture ( $)
66,000
13,500
0
213,825
°
Conventional Alternative
($)
513,000
61,000
0
1,180,950
Comment; The hyacinth system alone does not meet the total phosphorous discharge standard, therefore this cost
comparison deleted a unit process for phosphorus removal for the conventional alternative. Capital and 0
M & R cost are extremely high for mechanical treatment processes. Since a phosphorus removal unit proces:
would be required for each of the comparable systems, it can be inferred that the aquaculture technology
plus phosphorus removal process together, would be the most cost effective. Note that land was available
at no cost.
Reference: (8, 16, 17)
-------
Table 7.6
COST COMPARISONS BETWEEN AQUACULTURE AND
CONVENTIONAL TREATMENT ALTERNATIVES
Case Study No. 4
Location:
Description:
Hyacinth demonstration project - Lake Helen, Florida
Upgrade primary effluent like (synthetic wastewater) by hyacinth system (including methane recovery)
to meet stringent design effluent standards.
Operating Conditions
Average Flow: 26.4 m3/d (.007 MGD)
4 Lagoons : 0.17 ha (0.41 ac)
Mean Depth : (1.1 m) 3.5 ft
M
O
Mean Effluent Quality (mg/1)
BOD5
TSS
TN
TP
Before
65
40
25
7
A - Estimated
AfterA
2
2
2
0.2
B - No Limitations
o
Permit
—
Facility Requirement:
Aquaculture
4 calcium bentonite lined hyacinth
lagoons in series
Methane recovery process
Conventional Alternative
Not Determined
Cost Item * Aquaculture ($)
Capital Cost: 4 Lagoons Cost $24
Yard Piping 5
Storage Building 15
Fencing 2
Digester Tank w/Insulation 4
Fabrication Costs 1
Compressor for Methane 2
pH Controller 5
Temperature Controller
Pressure Controls
Storage Tank (250 gallon) 1
Concrete Slab
Flow Metering 1
Conventional Alternative ( $)
,500 Not Determined
,000
,000
,500
,000
,300
,500
,000
500
500
,000
300
,200
-------
Tc ' •"
(cc
0, M & R Cost;
Revenues:
Present Worth:
* 1981
Level Meters 1,200
Harvesting Equipment 5,000
Pumps 1,500
Seeding and Mulching 600
Spare Parts & Misc. 500
Sub Total $77,100
Land (1.5 ac x 3000) 4,500
TOTAL $81,600
Electricity @ $0.08/kwh $ 1,500
Labor 8 hr/wk @ $10.00/hr 4,160
Fuel 10 gal/wk @ $1.50 gal 780
Laboratory @ $25/wk 1,300
Administrative 1,000
Chemicals 400
Miscellaneous 400
TOTAL $ 9,540
Methane value recovered
estimated 100 MBTU
@$10/MBTU 1,000
Not Determined
Summary: Performance data for this privately funded demonstration project are not available at this time because
the facility recently started operation. However, these costs nave been included because the capital
costs were the actual costs for the facility. The estimated O, M, and R costs are also provided. Note
that this facility includes methane generation.
Reference: (18)
-------
Table 7.7
COST COMPARISON BETWEEN AQUACULTURE AND
CONVENTIONAL TREATMENT ALTERNATIVES
Case Study No. 5
Location: North Study Area - Gilbert, Arizona
Description: A solar aquaculture process has been proposed to treat raw screened domestic wastewater.
Operating Conditions
Projected Flow; 6435 m3/d (1-7 MGD)
Facilities Requirement ;
Mean Water Quality
BOD5
TSS
Projected Influent
200
275
(mg/1)
Projected Effluent
10
10
H
to
Aquaculture
Lift Station
Static Screen
Faculative Cell
Aerobic Cell
Rotoscreen
Rapid Sand Filter
Chlorination
Composting
Conventional Alternative
Lift Station
Static Screens
RBC
Secondary Clarification
Chlorination
Digestion
Composting
Cost Item* Aquaculture ($) Conventional Alternative ($)
Capital Cost (annual) 420,000 434,000
O, M & R Cost (annual 95,000 163,000
Revenues 0 0
Total Annual Cost 515,000 597,000
i = 6-7/8%
Comment; The 201 facilities plan concluded that a solar aquaculture facility was more cost effective than an
RBC process. Note that land is available at no cost.
Reference: (19, 20)
-------
W
Table 7.8
COST COMPARISON BETWEEN AQUACULTURE AND
CONVENTIONAL TREATMENT ALTERNATIVE
Case Study No. 6
Location: North Regional Wastewater Treatment Plant - Shreveport, Louisiana
Description: Aerated lagoon followed by a three celled hyacinth pond proposed to treat raw domestic wastewaters.
Operation Conditions
Projected Plow : 26,500 »3/d (7.0 MGD)
Surface Area : 26.6 ha (66 ac)
Depth : 1.2 m (4.0 ft)
Detention Time : 10 days
Average 8005 Loading: (85.1 kg/ha-da)(76 Ib/ac-da)
Facilities Requirement:
Mean Water Quality (mg/1)
BOD5
TSS
A - Not
Projected
Lagoon Effluent
86
A
Available
Permit
30
30
Aquaculture
Aerated lagoon followed by a
3 celled hyacinth pond
Chlorination
Cost Item*
Capital Cost
O & M Cost
Present Worth
* i - Not Available
Conventional Alternative
Race track oxidation ditch system
Chlorination
Aquaculture ( $)
5,322,000
223,000
7,890,000
Conventional Alternative ($)
5,903,000
236,000
8,342,000
Comment: The 201 facilities plan concluded that an aerated lagoon followed by a three celled hyacinth pond was
more cost effective than a race track oxidation ditch system.
Reference: (21)
-------
Location:
Table 7.9
COST COMPARISON BETWEEN AQUACULTURE AND
CONVENTIONAL TREATMENT ALTERNATIVES
Case Study No. 7
Hornsby Bend Sludge Treatment Plant - Austin, Texas
Description: Proposed upgrading and covering of existing hyacinth pond for the partial treatment of sludge from
three area wastewater treatment plants.
Operating Conditions
None Available
Facilities Requirement:
Mean Water Quality Data
None Available
Aquaculture
Conventional Alternative
Modify existing hyacinth
pond (earthwork)
Greenhouse
Disposal Equipment
Pump supernatent liquor to Onion Creek Plant
(plant must be sized larger than aqua culture
alternative)
Cost Item*
Aquaculture ($)
Conventional Alternative($)
Capital Cost
O, M, & R
Present Worth
* i - Not Available
893,875
Not Available
Not Available
1,232,452
Not Available
Not Available
Comment: The 201 facilities plan concluded that upgrading and covering the existing hyacinth pond was more cost
effective than pumping digester supernatent at the Hornsby facility back to the enlarged Onion Creek
Wastewater Treatment Plant. Example of aquaculture for sludge management.
Reference: (22)
-------
To upgrade the stabilization pond effluent to meet effluent limits of 30 mg/1
BOD and suspended solids the following alternatives were considered:
Water Hyacinth Aquaculture System
Intermittent Sand Filtration System
Microscreen or Rapid Sand Filter
The following critical site specific variables were assumed:
Design Flow: 0.5 MGD
BODe raw wastewater: 200 mg/1
Exisnng final stabilization pond effluent quality: 30 mg/1 BOD, 90 mg/1 SS
Existing system is already at maximum organic loading: 165 kg/ha/d
(150Ibs/ac/d) for facultative lagoon, 38.5 kg/ha/d (35 Ibs/ac/d) for final
stabilization pond
No chlorination requirement for final effluent
30.5 m (100 ft) buffer area fencing requirement
Additional land must be purchased at $1600/ha ($4,000/ac)
Site layout provides gravity flow from final stabilization pond
Clay soils
Solids handling not desired
Operators salary including benefits: $18/hr
Electrical cost $0.10/kw hr
Interest rate 7-5/8%
Engineering administration contingency: 25%
Three different options were considered for the water hyacinth alternative due
to variable Texas regulatory requirements which, depending on location, may
require either a lagoon cover or a liner. These options were:
No liner or cover requirement
Liner requirement, no cover requirement
Cover requirement, no liner requirement. (A system with a liner and
cover requirement was not considered.)
The hyacinth alternative was formulated from available design criteria published
by the Texas Board of Health ' and best engineering judgement. The
following criteria was used as the basis of the water hyacinth facility
alternative:
Hydraulic loading: .08 MG/ha/d (0.2 MG/ac/d)
Maximum basin size: 0.40 ha (1.0 ac)
Max basin width: 9.1 m (30.0 ft)
Water depth: 0.61 m (2.0 ft)
One additional basin required for emergency back-up
7-15
-------
The resulting system consisted of four hyacinth basins in series, each with a
surface area of 368 m x 9 m (12101 x 30'). An additional 4.6 ha (11.3 ac) of
land is required to be purchased. Minimal daily operator attention (1 hr/d) is
assumed. The hyacinths are to be harvested once per year with a rented front
loader and dried on-site. No further by-product utilization is assumed.
The estimated cost of the hyacinth alternative is presented in Table 7.10. As
shown, the liner requirement would add approximately $66,000 to the capital
cost. The cover requirement would add an estimated $1,187,500 to the capital
cost and would need to be replaced in 10 years.
Intermittent Sand Filter Alternative - The design for the intermittent sand filter
alternative was based on available design criteria and best engineering
judgement. The following criteria was used as the basis of this alternative:
Hydraulic loading: 0.2 MG/ha/d (0.5 MG/ac/d)
Filter drying time: 2 days
Operating depth: 1.07 m (3.5 ft)
The resulting system would consist of 3 filter beds, each with a surface area of
110 m x 36.6 m (360T x 120'). Additional land (3.03 ha (7.5 ac) purchase is
required to accommodate the filter beds. The daily estimated operator attention
is assumed minimal at 1 hr/d. The top 2 inches of sand are to be removed,
and replaced every 45 days with a rented tractor.
Table 7.10 shows the estimated cost of this alternative compared to the
aquaculture alternative.
Microscreen or Rapid Sand Filter Alternative - From a cursory design analysis
the microscreen or rapid sand filter alternatives were determined to have
roughly the same cost and are therefore presented together. The following
criteria was used as the basis for this alternative:
2 2
Hydraulic loading (microscreen): 1.02 1/m -s (1.5 gpm/ft ) net effective
submerged area „ 2
Hydraulic loading (rapid sand filter): 1.36 1/m -s (1.5 gpm/ft ) surface
area
2-day holding tank required for emergency by-pass cover requirement.
Cover required.
7-16
-------
Table 7.10
ESTIMATED COSTS FOR SELECTED ALTERNATIVES:
HYPOTHETICAL CASE STUDY
Costs
Capital*
Land
Total
0, M, and R
Labor
Energy
Chemicals &
Materials
Replacement
Total
Present
Worth**
Hyacinth
No Liner
No Cover
123,000
45,500
168,500
12,000
0
0
3,000
15,000
301,500
Alternative
Hyacinth Hyacinth
Liner No Liner
No Cover Cover
189,000
45 , 500
234,500
12,000
0
0
3,000
15,000
367,500
1,310,000
45,500
1,355,500
12,000
0
0
3,000
15,000
1,488,500
Intermittent
Sand
Filter
434,500
30,000
464,500
14,500
0
9,500
8,500
32,000
781,000
Microscreenor
Rapid Sand
Filter
290,000
0
290,000
10,000
4,500
500
6,000
21,000
502,500
* Includes 25% for Engineering, Administrative, Contingencies
** i = 7-5/8%; Salvage for land only.
7-17
-------
The resulting system consisted either of a 3.0 m (10 ft) diameter by 4.9 m (16
ft) tnicroscreen or a 1.8 m by 11.0 m (61 x 36') rapid sand filter (automatic
back wash). It was assumed that the unit process could be placed on existing
owned land and additional land was not necessary. Because the existing plant
is being loaded to the maximum BOD. level, the facultative lagoon surface must
D
be enlarged by 0.52 ha (1.3 ac). The microscreen or rapid sand filter are
more mechanically" complex than the other two alternatives, so additional daily
operation attention was considered.
Table 7.10 compares the estimated costs of this alternative with the other
alternatives in this hypothetical situation. The U.S. EPA guidelines for
(9)
determining cost-effectiveness were followed.
From this hypothetical design process the following variables were observed to
have an influence on the cost of the hyacinth alternative and therefore also
influence the ranking of alternatives.
Quantity of flow
Design influent water quality parameters
Design effluent water quality parameters
Land cost
Land availability
Climate, geology, topography, soil type
Electrical cost
Desired solids handling method, growth rate
Skill and salary of available operator
Requirements of governing regulatory board
liner
cover
buffer zone
emergency back-up uints
others
Current loading on existing unit processes
Salvage value
Interest rate, engineering, administrative, contingencies
Revenues from by-product,if any.
As can be seen in Table 7.10, four hyacinth lagoons in series with no liner or
cover would provide the most cost-effective alternative in terms of present
worth, even though there is a requirement for purchase of additional land.
While this situation is extremely site specific, this case study presents the
7-18
-------
variables that can influence the cost of APU's and should be of value to
planners.
The next most cost-effective alternative would be lined hyacinth lagoons. As
shown in the comparison, the high cost of covering hyacinth lagoons to achieve
continual year-round growth can have an adverse effect on cost-effectiveness.
The intermittent sand filter alternative has comparatively higher costs due to
piping and other materials costs. Operating costs are comparatively high due
to sand replacement cost and greater labor involvement with removing, and
replacing filter media.
The rapid sand filter or microscreen alternative is less cost-effective in terms
of present worth than the uncovered hyacinth alternative regardless of the
additional land cost for the hyacinth alternative. This is due to higher
equipment cost and the solids handling problem which required enlargement of
the existing facultative lagoon. Labor costs are less for this alternative
compared to hyacinth aquaculture, but energy and replacement costs would be
higher.
It must be noted from this hypothetical example that, while aquaculture can be
cost-effective, site specific conditions may cause more conventional technologies
to be more favorable. It can also be inferred that aquaculture probably has its
greatest application in areas where land is available at low cost and where
regulatory or physiographic limitations do not force the use of components like
lagoon liners, covers or other items which can significantly affect costs.
Finally, it is apparent that if a by-product can be harvested and marketed to
produce revenues, cost-effectiveness can be enhanced.
7.2 Summary
Although meaningful economic comparisons between wastewater aquaculture
technologies and conventional technologies are difficult to derive at this stage of
aquaculture development, case studies for certain existing facilities indicate that
aquaculture technology can be a cost-effective, low-energy alternative which
provides a satisfactory quality effluent. Recent wastewater facility plans are at
least considering wastewater aquaculture, and some have concluded that
7-19
-------
aquaculture technology is cost-effective compared to conventional alternatives.
Economic comparisons between wastewater alternatives must be based on site
specific variables for each contemplated application.
7-20
-------
REFERENCES
1. Middlebrooks, E.J. and C.H. Middlebrooks, "Energy Requirments for Small
Flow Wastewater Treatment Systems", EPA MCD-60, 1979.
2. Tchobanoglous, G., et al, "Energy and Resource Consumption in Land and
Aquatic Treatment Systems In: Proceedings of the U.S.D.O.E. Energy
Optimization of Water and Wastewater Management of Municipal and
Industrial Applications Conference. Argonne National Lab.
ANL/EES-TM-96, 1979.
3. Bastian, R.K. "Natural Systems in Wastewater Treatment and Sludge
Management: An Overview", Unpublished Report, Office of Water
Program Operations, U.S. EPA.
4. Crites, R.W., "Economies of Aquatic Treatment Systems" Aquaculture
Systems for Wastewater Treatment: Seminar Proceedings and
Engineering Assessment. EPA 430/9-80-006, September 1979.
5. Lee, C., and T. McKim, "Water Hyacinth Wastewater Treatment System",
Undated-Unpublished, Reedy Creek Utility Company, Lake Buena
Vista, FL.
6. Reed, S.C., et al, "Engineers Assess Aquaculture Systems for Wastewater
Treatment", in Civil Engineer - ASCE, Vol. 51 No. 7, 1981.
7. Fritz, W.R., and S.C. Helle, "Cypress Wetlands for Tertiary Treatment",
Aquaculture Systems for Wastewater Treatment Seminar Proceedings
and Engineering Assessment. EPA 430/9-80-006, September 1979.
8. Innovative and Alternative Technology Assessment Manual, EPA Publication
No. 430/9-78-009, 1978.
9. Title 35 Appendix A.6 and (6.507(c)(5),(.6)(7))
10. Design Criteria for Sewerage Systems - Rules 301.79.05.001-.013, Texas
Department of Health Wastewater Surveillance and Technology, 1981.
11. Wolverton, B.C., and R.C. McDonald, "Upgrading Facultative Wastewater
Lagoons with Vascular Aquatic Plants" WPCF, Vol. 51. No. 2, 1979.
12. Wolverton, B.C. and R.C. McDonald, "Vascular Plants for Water Pollution
Control and Removable Sources of Energy" In: Proceedings
Bio-Energy '80 World Congress and Exposition, 1980.
13. Wolverton, B.C., Personal Communication: N.S.T.L., NASA, Bay St.
Louis, MS., 1981.
14. Williams, T.C., and J.C. Sutherland, "Engineer, Energy, and
Effectiveness
7-21
-------
Features of Michigan Wetland Tertiary Wastewater Treatment Systems",
Aquaculture Systems for Wastewater Treatment. Seminar Proceedings
and Engineering Assessment. EPA 430/9-80-006.
15. Yardley, B., Personal Communication: Houghton Lake Sewer Authority,
Houghton Lake, Michigan, 1982.
16. Sewett, D., "A Water Hyacinth Advanced Wastewater Treatment System",
Aquaculture Systems for Wastewater Treatment. Seminar Proceedings
and Engineering Assessment. EPA 430/9-80-006, 1979.
17. Christian, K. Personal Communication: Gee and Jensen Engineers, Inc.,
Orlando, Florida, 1981.
18. Stewart, E.A. Ill, Personal Communication: Amasek, Inc., Hudson,
Florida, 1982.
19. 201 Facility Plan for Wastewater Management System for Gilbert, Arizona,
Moore, Knickerbocker & Associates, Inc., 1980.
20. Moore, Knickerbocker and Associates, Inc. Personal Communication,
Phoenix, Arizona, 1981.
21. 201 Facility Plan for Shreveport, Louisiana, Black & Veatch,
Inc.
22. Supplement to the GovaHe Wastewater Treatment Plant Facility Plan,
Innovative and Alternative Technology, Hyacinth Cover for Year
Round Protection, City of Austin, Texas, 1980.
7-22
-------
CHAPTER 8
BY-PRODUCTS DERIVED FROM WASTEWATER AQUACULTURE
8.0 GENERAL
A significant deterrent to the aquaculture industry in the United States is in
the harvesting, processing and marketing of cultured species from clean waters
and in obtaining consumer acceptability for those products. Development of a
new industry often progresses from the elimination of technical problems in
production to the development of markets, once a marketable product has been
achieved. In many cases clean water aquaculture in the United States is
between these stages, where a product is finally available in sufficient
quantities for market, but the producer lacks sufficient manpower, capital, time
and market information to successfully develop the available markets. Without
successful marketing procedures, it is virtually impossible to make consumers
either aware of or receptive to new products.
Considering that wastewater aquaculture is a limited segment of the aquaculture
industry, the problems encountered in the processing and marketing of the
products and in obtaining consumer acceptance of the marketed product are
severely compounded. The greatest constraints reside in the potential
contamination of the waste-grown aquaculture product by disease-causing
organisms or toxic and/or carcinogenic substances, and a generally negative
(9)
psychological response by humans toward any items derived from wastewater.
Thus, added to the operational barriers of the aquaculture industry as a whole,
are the legal and emotional barriers which limit the acceptability of food and
fiber products derived from wastewater aquaculture.
8.1 Potential Uses of Aquaculture Products Derived from Wastewater
8-1
-------
At the present time, the primary concern of wastewater aquaculture in the
United States is the production of clean water. However, by their very
nature, aquaculture systems create secondary products other than clean water,
namely the aquatic species which are cultured. The secondary products can be
viewed in two ways: either simply as a by-product of the treatment process
which must be disposed of, much as sludge in conventional treatment processes,
or as a useful co-product of the treatment system, which has some commercial
or social value. Examples of both can be found in current wastewater
aquaculture technology. The domestic wastewater treatment facility at Benton,
Arkansas cultures silver and bighead carp in combined aquaculture-based
treatment lagoons. Harvested fish from this facility are disposed of by burial,
even though analysis of the processed fish flesh has indicated that
contamination above the U.S. Food and Drug Administration rejection levels does
not exist .
Other wastewater aquaculture systems have experimented with by-product
(34)
utilization, primarily using harvested vegetation as animal feed supplements,
or after composting, as a soil amendment. As an example, the demonstration
wastewater hyacinth system at Walt Disney World, Florida currently composts
harvested water hyacinths by the static pile method and allows them to
decompose without further turning or processing. The stabilized end-product
is transported to an ornamental tree farm where it is applied as a soil
(2)
amendment and supplemental nutrient source .
Many different uses for the by-products of wastewater aquaculture systems
have been identified. Each use encounters a variety of different constraints;
some of them obviously being more sensitive than -others.
8.2 Food for Direct Human Consumption
There currently exists a potential for the production, marketing, and
consumption of aquaculturally grown products in the United States. This is
evident in the fact that U.S. consumption of freshwater and seafood products
(3)
exceeds the rate of production and large quantities are imported from foreign
countries each year. Foreign import dependence could be decreased if domestic
fish and shellfish production could be increased through utilization and
recycling of the nutrients found in many biological wastewaters.
8-2
-------
(35)
Suffer-n et al (1981) reports that current estimates of production from the
phytoplankton-bivalve mollusk food chain system developed at Woods Hole
indicate that a wastewater aquaculture system treating the domestic waste of a
town of 50,000 could potentially produce an annual crop of over 900 tons of
oysters, a valuable seafood crop.
The largest single operating expense to fish culturists is the cost of feed for
(4)
high density culture. Accordingly, any acceptable and inexpensive feed
supplement becomes economically attractive. Hephner and Schroeder
demonstrated that organic wastes applied to fish rearing ponds stimulated an
increase in natural food sources (zooplankton and chironomids) available to fish.
Thus, the incentive to use wastewaters in fish culture is clear. The most
significant deterrent to this practice is the concern that pathogenic
micro-organisms and other potentially harmful wastewater constituents which
coexist with the beneficial nutrients may be bio-accumulated and concentrated in
( R ^
the fish and passed on to consumers. Carpenter, et al investigated
microbial pathogens in sewage and sewage-grown fish in a six-cell lagoon system
in Quail Creek, Oklahoma. Three pathogens were identified in the raw sewage
influent but none were found beyond the second cell (which did not contain
fish), and pathogens could not be isolated in any of the 179 fish sampled.
(35)
Suffern et al., studied bioaccumulation and biornegnification of heavy metals
in raw wastewaters at Oak Ridge National Laboratory in a two-pond food chain
polyculture wastewater aquaculture system where tilapia were suspended in cage
culture. Those metals studied; Cd, Cr, Cu, Ni, Pb and Zn tended to decrease
in concentration at higher trophic levels. They also found the major reservoir
of heavy metals to be the bottom sediments or sludge in the systems. Suffern
suggests that the tilapia cultured may be increasing in weight and size faster
than they can accumulate metals, thus diluting the heavy metal concentrations
in the fish flesh. In addition, the high concentrations of organic complexes
present in the water may also explain the low metal accumulation rates in higher
trophic levels.
The direct use of wastewaters in ponds with active fish culture is perhaps the
most sensitive practice in terms of contaminants being taken up by harvested
organisms. The further the wastes are separated from the product, the less
8-3
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sensitive to contamination the product should become. The concept of
polyculture may well suit this separation requirement. Poly culture systems
include the culture of several organisms in a food chain; one organism being
cultured as a food source for another, and that organism cultured and
harvested for another, and so on, until the final product is obtained. This
idea, as diagrammed in Figure 8.1, has been the subject of research at Woods
Hole Oceanographic Institute in marine (mariculture) food chains and has
proven a promising, but more costly alternative.
A somewhat analogous concept is that of raising bait minnows in wastewater
facilities. The minnows would be a lucrative product that would never be
directly consumed by humans.
Another approach to obtaining valuable and acceptable fish by-products from
wastewater aquaculture would be to provide for only a portion of the life cycle
of fish in the wastewater aquaculture facility. Fish would be reared for only a
portion of their life cycle in a wastewater aquaculture environment and then
transferred either to a clean-water aquaculture facility or natural clean-water
environment for a period of time which allows both significant growth and
depuration. Depuration would greatly reduce the potential risks to human
consumption and there would also be a potential to improve the quality of the
fish product through controlled feeding and diet. In Michigan and Wisconsin
there have been efforts to rear fingerling game fish, like the muskellunge, in
wastewater facilities, for eventual release. While sport fish rearing in public or
industrial wastewater facilities might not produce direct monetary returns,
donation of sport fish for stocking public waters would result in certain public
relations benefits and would free state facilities from rearing of fingerling sport
fishes.(36)
Additionally, rearing of Gambusia or mosquito fish in wastewater aquaculture
facilities may be a socially and commercially valuable product in regions where
mosquito control is important. Gambusia can be sold to mosquito control
districts for stocking in mosquito habitat.
The harvesting and processing of plant biomass from a wastewater aquaculture
system can lead to indirect by-product utilization for human consumption.
8-4
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Figure 6.1
FOOD CHAIN POLYCUl/TURE{7*
Phytoplankton
Brine Shrimp
Fin
fish
I
Phy top lank ton
Filter
Molluscs
Crustaceans
Carnivorous fish
Lobster
Shrimp
Seaweeds
«.
Nitrogen-
Depleted
-------
Indirect uses encompass waste-grown plants as feed for cattle or poultry, which
are ultimately used for human consumption.
If the safety of aquaculture by-products grown in wastewater supplied systems
can be assured then, the further question of consumer acceptability must be
addressed. Consumer acceptability can be influenced to a significant degree by
imposed regulatory constraints in marketing the products, governmental support
of product purity, and educational support in advertising.
Wastewater aquaculture products for human consumption face serious legal
obstacles from enforcement of the 1938 Food, Drug and Cosmetic Act which is
concerned with "adulteration11 and "misbranding". Huguenin and Little
addressed the legal and political problems encountered for waste-grown aquatic
foods under this regulation. They indicate that waste-grown aquatic foods can
be easily condemned under the broadly interpreted phrase in the law: "consists
in whole or in part of any filthy, putrid or decomposed substances", or "is
otherwise unfit for food". In addition, they discuss the inconsistencies between
regulations over substances occurring "naturally" in foods, and those
intentionally or unintentionally added to foods by man.
With respect to naturally occurring substances, it is important to emphasize that
researchers have suggested that high productivity in estuarine environments
could, at least in part, be due to the increased nutrients discharged from
sewage treatment plants in coastal areas. Aquatic foods derived from these
areas would be condemned only in the case where they were demonstrated to be
dangerous to health. In the case of wastewater aquaculture food products, the
same substances would be perceived as "added intentionally" by man, and thus
(9)
the products condemned if there were any concern over health hazards .
With respect to "misb ran ding" waste-grown aquatic foods, if the wastewater
aquaculturist is required to explicitly label the products as being derived from
wastewater sources, it is obvious that the negative impact on consumer
acceptability will be great. On the other hand, if concerned regulatory
agencies endorse the safety of the products, and participate in the educational
8-6
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advertising which supports the proven quality; it may be more acceptable to the
consumer by reducing the psychological barriers.
8.3 Soil Amendments, Fertilizers and Compost
The use of wastewater aquaculture by-products as soil amendments, fertilizers
and composts represents perhaps the least sensitive alternative in terms of
public health and consumer acceptability. However, it also represents an
alternative which could provide the least economic return. Bruhn and
Koegel studied the utilization of harvested Eurasian watermilfoil and
filamentous algae as soil conditioners and fertilizer and found that the economic
return of the products would cover only 10 percent of the harvesting costs.
When assessing the market value of water hyacinths as compost, Robinson et
(12)
al, found that the compost value of hyacinths was comparable to peat moss
compost, but that a defined market for composts per se, was not identifiable.
(13}
Conversely, Bagnall et al., found that water hyacinth compost could be
produced at a cost of $3 per ton, and sold for $46/ton to "a readily developable
market of nurserymen and home gardners".
Currently, the discussion of wastewater aquaculture by-products utilization for
composts, fertilizers and soil amendments has centered around the use of
aquatic vegetation. Much research has been devoted to the water hyacinth and
its nitrogen, phosphorus and potassium content, its water retention value and
processing needs for ease of handling and transport. Research in these areas
utilizing other wastewater aquaculture plant species is necessary, as the
economical use of water hyacinths in these systems is limited to geographic
locations where climate is suitable.
The fertilizer value of aquatic plant species is highly variable; being influenced
by processing methods, stage of growth, nutrient availability in the water body
(12)
in which it is grown, to mention only a few. Robinson et al., found water
hyacinths to have an average primary nutrient content of 1.61 percent N, 0.71
percent P00_, and 4.59 percent K_O, which compared poorly to the
i 0 Ct
concentration of the same nutrients in commercially available mineral fertilizers.
However, an important characteristic to consider when comparing processed
water hyacinth with mineral fertilizers, is that water hyacinths represent an
8-7
-------
organic fertilizer source, which releases nuturients to the soil over a period of
f 14)
time. Mineral fertilizers, on the other hand, are applied in the available
form for plant uptake, a highly soluble form which is extremely vulnerable to
loss from system due to leaching.
Aquatic vegetation is not the only by-product of wastewater aquaculture
systems with potential fertilizer value. Processed liquified fish emulsions are
currently being used as organic fertilizers on croplands. As organic
farming practices increase, and petroleum based mineral fertilizers escalate in
price, the use of natural fertilizers such as this is expected to increase. A
local organic fertilizer market has already been delineated for the expected
yearly harvest of fish from a proposed finfish wastewater aquaculture system
f\R\
for the Town of New Castle, Virginia. The tentative plan involves an
enzymatic anaerobic liquid digestion process for the harvested mosquito fish
(Gambusia) and fathead minnows to obtain a fish-emulsion fertilizer product
valued at 50*/gal. The marketing of this product will involve emphasis of
its benefits as a replacement liquid nitrogen, lower comparative cost, and
benefit to the soil, because liquid nitrogen depletes the organic content of
soils, while the fish emulsion would actually improve organic content.
While the fertilizer value of aquatic plants and animals is admittedly less than
conventional mineral fertilizers, several other benefits are associated with the
use of organic fertilizers derived from wastewater sources. Harvested
vegetation and organisms are by-products of the production of clean water;
therefore, essentially they represent an opportunity cost. If they are disposed
of in a landfill or by other conventional means, the products represent a
treatment cost. If the harvested vegetation is allowed to naturally decompose to
compost and the product is given away it still represents a cost savings to the
wastewater aquaculture operator, because there will be no cost incurred for
appropriate transportation and disposal. On the other hand, if there is a
defined market for the by-product, given a slightly greater capital investment
initially to upgrade the quality of the product by investing in approprite
processing devices, such as an anaerobic digester, then a greater economic
return from the sale of the by-products to offset the treatment costs could be
realized. Not only would users of wastewater aquaculture benefit from the
8-8
-------
recycling of fertilizer nutrients removed from the wastewater and added to the
by-products; the by-product consumer would benefit as well. The use of
composts as soil amendments, conditioners and fertilizers in the place of mineral
fertilizers benefits the soil by not only increasing the organic matter content
and water holding capacities, but also by reducing rainfall runoff and erosion
impacts and evaporation from the soil surface.
8.4 Fiber
Harvested aquatic macrophytes cultured in wastewater aquaculture systems
represent a potentially valuable fiber resource for use in many different
consumer products. To date, the most popular fiber-use investigated for a
wastewater aquaculture by-product has been the processing of water hyacinths
for pulp and paper manufacturing. Unfortunately, the results of various
studies consistently indicate that the water hyacinth has minimal application
x 4 rr \
potential for paper production. Nolan and Kirmse describe several
characteristics of the water hyacinth that make it uneconomical to use as a pulp
material or in blends. They include:
Low freeness value in water hyacinth pulp and in pulp blends
compared to pine kraft
Very slow drainage compared to pine kraft pulp
Low tear factor
Low yield
Poor appearance
(12)
Robinson et al. attribute the poor paper manufacturing qualities of water
hyacinth to its bulkiness and high water absorbency. They suggest the
hyacinth may be more suitable in other products that would benefit from the
plants high adsorbency characteristics, such as disposable diapers.
While the hyacinth has been demonstrated to be troublesome and uneconomical to
use in paper manufacture, other aquatic macrophytes could prove to be more
suitable for pulp production. Reeds, sawgrasses and cattails have been
suggested as fiber sources for pulp. Through the use of the reed, Phragmites
communis, Romanian manufacturers have addressed a significant aquatic reed
(18)
problem and the decline in availability of wood for paper manufacture. The
8-9
-------
reeds are harvested from the Danube River basin annually at a rate of about
(14)
125,000 tons and are converted to pulp for use in blending with wood pulp
Several paper products, fuels, synthetic fibers and fertilizers are some of the
reported end-products that result from full utilization of reeds in Romania.
(18)
Rudescu recommends the utilization of sawgrasses in the same manner as
Phragmites communis, due to their similar characteristics.
(14)
The National Academy of Sciences assessment of the potential use of cattails
(Typha spp.) as a source of pulp, paper and fiber is very optimistic. Though
there has been no current assessment of pulp production potential or suitability
for paper there is historical precedent for use of cattails in paper production.
(14)
The National Academy of Sciences (NAS) notes that books were produced in
the eighteenth century that contain pages made from cattail paper. The
assessment also notes that cattails are suitable as a weaving or caning material
(19)
in mats, baskets, and furniture. also mentions the application of the reed,
Seirpus spp., for use in wicker furniture in West Germany.
8.5 Biogas Production
The bioconversion of wastewater aquaculture plant biomass to produce methane
gas has been suggested as an appropriate by-product use for wastewater
aquaculture systems. Depending on the scale of the facility, methane may or
may not be produced in sufficient quantity to become a saleable by-product. In
certain cases, the volume produced may only be sufficient to heat digesters to
optimum methane production temperatures or possibly for a few other on-site
uses. Digester sludge, however, may be a marketable by-product of the
anaerobic digestion process as it can be used as a fertilizer product.
Methane production in anaerobic digestion processes. can be influenced by a
variety of factors of which, the C:N ratio of the digester material is most
important. Wolverton et al., reports that water hyacinths maintain a
desirable C:N ratio of 23:1 for maximum methane production. Other factors
such as lignin content also affect the suitability of a given plant material for
anerobic digestion to produce methane gas. The lignin content of plants is
important in that this particular cellulosic compound is very difficult to
biodegrade and will affect the quantity of methane production. While water
8-10
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hyacinths have a low lignin content, generally, most marsh plants have a higher
(21)
lignin concentration and are less suitable.
The anaerobic filter process has been developed for high rate anaerobic
digestion using water hyacinths at the National Space Technology Laboratories
( 22)
(NSTL) in Mississippi. In bench scale studies using this method, maximum
3 3
methane yields of 3.17 ft lib dry weight for water hyacinths and 2.34 ft lib
dry weight for water pennywort were achieved. During this study, it was also
found that the anaerobic filter performed most efficiently after several uses.
Temperature during the experiments was maintained by an incubator at 37°±1°C.
In full scale operation, temperature may prove to be a significant constraint to
this bioconversion method. Conventional digesters lose heat through several
different pathways, through the walls, floor and roof of the digester, which
will have to be compensated for in digester heating. The energy expenditure
in maintaining the digester temperature may offset the energy gain in methane
production. In addition, the methane produced in the digestor is not readily
useable, and contains carbon dioxide, hydrogen sulfide and other contaminants
which must usually be removed prior to burning the gas.
In summary, the initial outlook for bioconversion of wastewater aquaculture
plant biomass to methane gas may have been too optimistic in terms of quantity
and widespread applicability to wastewater aquaculture systems. The seasonal
variation in plant biomass production in different climates will also affect
anaerobic digestion applications. Low-temperature gasification (pyrolysis) has
been suggested as an alternative to anaerobic digestion for energy production,
but extensive data on this method has not yet been made available for
( 23)
evaluation.
8.6 Feeds and Feed Supplements
The potential for aquatic plant biomass processed for use as animal feeds and
feed supplements is very optimistic. Nutritionally, several aquatic plants
investigated thus far have been found comparable to terrestrial plants commonly
used for roughage in ruminant diets. While much research again has been
centered around the water hyacinth, additional investigation is necessary for
other aquatic plant species to determine their value in livestock feed
8-11
-------
applications. Experience in removing water through pressing, solar drying and
other methods has indicated that dewatering is a technical and economic
constraint to utilizing wastewater aquaculture plant biomass for animal feeds and
feed supplements.
The nutritional value of several species of aquatic plants that have been grown
in wastewater aquaculture systems have been evaluated to assess suitability for
use as animal feeds and feed supplements. In addition, fish harvested from
wastewater aquaculture systems may also have value as fish meal similar to
menhaden meal which is currently used as a protein supplement in livestock
feeds.
Much of the published research pertains to the water hyacinth and its
nutritional value, acceptability (processed and unprocessed) and its value in
silage for livestock feed. And, it can be concluded that water hyacinths are
suitable feed supplements (dried or ensiled) for ruminant animals. Possible
constraints to using water hyacinths in cattle or sheep diets involve mineral
content, palatabiMty, ash content, and protein content.
(24)
Table 8.1 shows the mineral content reported by Easley and Shirley for
water hyacinths. The concern over minerals involves the possibility of mineral
imbalances which might be caused due to the relatively high degree of these
substances in dried, pressed and ensiled water hyacinths compared to
conventional livestock feeds. Palatability problems arise when cattle are fed
dried, ensiled water hyacinths alone. However, when hyacinths were ensiled in
combination with citrus pulp or molassas, the feed was readily accepted by
(12)
cattle. High ash content in hyacinth feeds appears to reduce gross intake
by livestock and therefore could affect growth rate. The protein content of
water hyacinths has led some researchers to conclude that supplemental protein
(12)
is necessary in livestock diets where processed water hyacinths are used.
Several species of the duckweed family (Lemnaceae) have also been analyzed for
their protein content to assess the potential of using duckweed species in animal
feeds. While species of Lemna, Spirodela and Wolffia have not been as
intensively investigated as the water hyacinth in this regard, initial studies
have indicated that they are acceptable as animal feed sources. Culley and
8-12
-------
Table 8.1
CONCENTRATION OF MINERAL FEED NUTRIENT
EU2MENTS REPORTED BY EASLEY AND SHIRLEY
FOR WATER HYACINTHS(24>
Element Average
Calcium
Phosphorus
Potassium
Magnesium
Sodium
Iron
Copper
Zinc
Manganese
Chromium
High
Low
Percent, Dry Basis
2.2
0.50
4.1
0.59
0.94
2.7
0.66
6.4
0.64
1.20
2.0
0.17
1.0
0.52
0.62
mgAgr Dry Basis
1,701
12
43
142
3.2
3,183
30
71
227
10.6
522
7
30
106
-0-
8-13
-------
(25)
Epps characterized the positive animal feed aspects of the various duckweed
species to include:
relatively easy harvesting
low fiber and lignin content
high mineral absorptive capacities
few pests
extended growing season
Experimentation with duckweed feeding trials has demonstrated that duckweed
use in poultry diets actually increased growth rates as compared to conventional
(OR)
feeds. Swine have also been fed unprocessed duckweeds successfully. The
nutritional analysis of domestic wastewater-grown Spirodela oligorhiza is
provided in Table 8.2 as compared to several conventional animal feeds.
A vitamin evaluation of the pondweed (Potamogeton foliosis) harvested from the
Deshler, Ohio sewage treatment lagoon was conducted to assess its value as a
fyci\
vitamin source in swine and poultry feeds. The evaluation indicated that
the sewage lagoon biomass vitamin content compared favorably to conventional
feeds, as demonstrated in Table 8.3.
In general, the greatest constraint to the use of aquatic plants as feed
supplements has been the excessive processing requirements which often involve
costly drying and additives to amend the final product.
8.7 Harvesting and Processing Wastewater Aquaculture Biomass
If by-product utilization is considered for an APU, efficient and economical
by-product harvesting and processing methods must be established. A wide
variety of harvesting techniques have been used in APUs. Generally, the
methods of harvest are influenced by the following variables.
type of biomass harvested
size and configuration of APU
amount of biomass present and desired rate of removal
skill of available operating personnel
8-14
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Table 8.2
NUTRITIONAL ANALYSIS OF WASTEWATER GROWN
SPIRODELA OLIGORRHIZA IN COMPARISON WITH
SEVERAL ANIMAL FEEDS T*
Feed Type
Duckweed***
(Spirodela oligorrhiza)
Alfalfa leaf meal
Coastal Bermuda grass
(dehydrated)
Corn (yellow)
Cottonseed meal
Milo maize
Oats
Peanut meal and hulls
(expeller)
Soybeans
Soybean meal (expeller)
Wheat bran
Proportion of Component
%
Protein Fat Fiber Ca P Ash
28.5**
20.0
14.0
8.8
41.0
9.0
12.0
45.5
37.0
42.0
14.5
5.5
3.5
2.0
3.8
4.0
2.5
4.0
6.0
18.0
3.5
3.0
11.8
21.0
28.0
2.5
13.0
2.7
12.0
12.0
5.0
6.5
11.0
1.3
1.45
0.50
0.01
0.15
0.02
0.10
0.15
0.25
0.20
0.10
1.0
0.27
0.20
0.25
1.20
0.27
0.33
0.55
0.58
0.60
1.15
17.7
10.5
6.0
1.5
6.5
1.7
3.5
5.8
4.7
6.0
7.0
*
**
***
Adapted from Culley S Epps (1973)
Crude Protein
Cultured in Domestic Wastewaters
(25)
8-15
-------
Table 8.3
COMPARISON OF SEWAGE LAGOON BIOMASS VITAMIN CONTENT WITH OTHER FEEDS
Vitamins
Biotin
B12
Choline
Niacin
Pantothenic
Acid
Total fi-
fe
Riboflavin
Thiamine
Feed Source (mg/kg dry weight)
Lagoon
Biomass
0.36
0.10
1020.00
30.00
13.18
1.35
19.81
5.00
Alfalfa
—
—
1550.00
41.90
20.90
6.50
10.60
3.00
Barley
0.20
—
1030.00
57.40
6.50
2.90
2.0
5.10
Sugar
Beet
—
—
829.00
16.30
1.50
—
0.70
0.40
Corn
0.05
—
550.00
20.00
5.00
5.0
1.10
—
Soybean
0.32
—
2743.00
26.80
14.50
8.0
3.30
6.60
8-16
-------
compatibility with end product utilization scheme
cost
The processing requirements of animals and plants harvested from APUs are
necessarily determined by the end-product desired.
8.6.1 Aquatic Plant Harvesting and Processing
Aquatic plant harvesting methods have been studied extensively, chiefly to
develop methods to combat nuisance growth of aquatic weed in waterways and
lakes. The results of research efforts have led to the development of
water-based mechanized harvesting equipment to remove vegetation from the
water and transport it to shore. The use of floating or barge-mounted aquatic
plant harvesting machinery is applicable for APUs where configuration does not
allow retrieval from land-based cutting and conveyor equipment.
Land based harvesting systems can be utilized for APUs systems that provide
sufficient land access to the unit. Several types of floating and land based
harvesting eequipment are commercially available. The water hyacinth culture
basins at Walt Disney World, Florida are designed to facilitate a land-based
(27)
harvesting, technique from the sides of concrete channels 360' x 29.
During harvesting the plants are manually guided with a hook to a conveyor
attached at the side of the channel. From the conveyor, the plants are passed
through a flail chopper, and the chopped plants are then piled. A similar
system that can be used in lagoons with broad surface areas uses a pusher boat
to guide hyacinths to a conveyor which is 1.52 m wide and 8.53 m long and has
(29)
a capacity of 9.2 tons/hr. A drag line bucket arrangement has also been
used to harvest water hyacinths and was found to provide simple and flexible
(29)
continual operation. Stewart reported the use of a pump with a cutter
element for hyacinth harvesting with a harvest rate potential of 2 tons/hr.
Dinges has proposed constructing harvesting platforms in hyacinth basins to
support harvesting machinery. The platforms are normally submerged but
water levels are lowered during harvesting to permit access by harvesting
equipment.
8-17
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Generally, aquatic harvesting equipment is a significant capital investment. A
practical solution to help mitigate the cost of the equipment might be to develop
harvester-sharing arrangements with local organizations (state, county or local
lake associations) that use aquatic weed harvesters to control overgrowth in
waterbodies. Such a situation exists in Plant City, Florida, where the state
loans its aquatic weed harvester to the treatment plant periodically to harvest
(33^
water hyacinths from their polishing ponds.
Duckweed is relatively easier to harvest than water hyacinths because of small
size and formation of dense floating mats. Commercially available screening and
skimming devices can be used for this purpose.
Other types of aquatic vegetation that are submerged or emergent can be
harvested through a variety of techniques that are both manual and mechanical.
Reeds, cattails and other emergents can be mechanically harvested with mobile
equipment or manually harvested with implements such as a scythe. Submerged
aquatic vegetation can be harvested mechanically with harvesters fitted with
cutter bars/31*
Subsequent to harvesting the aquatic plants, processing usually begins with
chopping or shredding the plants to reduce volume for easier handling and
transport. The amount of further processing is determined by the end product
desired. After chopping, plants destined to be used as soil amendments can be
applied directly to the soil to take advantage of high moisture content, or piled
and allowed to decompose. Chopping and blending into a slurry is required for
plants which are to be used in an anaerobic digester to produce methane
(22)
gas. Further processing for biogas production involves labor inputs in
monitoring and controlling the digester and the remaining accumulated sludge.
Chopping is also required for those plants destined for pulping processes used
in paper manufacture.
Several other by-product utilization schemes including use in animal feeds and
feed supplements require the drying of aquatic vegetation. Drying beds similar
to those used for sludges resulting from conventional treatment processes can
be used, however, they require land adjacent to the already land-consumptive
treatment plant. There have also been experiments with solar greenhouse
8-18
-------
pulp, and other substances has been practiced to improve palatability to
(12)
(3-)
dryers. ~ Severed different types of presses have also been used to reduce
water content. However, after pressing, moisture content is still significant
and the extracted liquid, which contains solids, nitrogen, and phosphorus,
becomes a waste which must be recycled through the API) or otherwise used.
Additional drying techniques which follow pressing have involved rotary
(12)
dehydrators, fixed or traveling bed dryers and air-agitated dryers.
Ensiling dried aquatic vegetation with sugarcane, molasses, corn hulls, citrus
pulp, am
livestock.
8.8 Harvesting and Processing Aquatic Animals
The technology for aquatic animal harvesting has been well-developed by the
clean water aquaculture industry and can be applied to the harvest of
organisms cultured in APUs. As with aquatic plants, the equipment and
harvesting techniques used for removal of aquatic species are again dictated by
the type of animal and the size and configuration of the basin in which they are
cultured. The devices used to harvest fish in lagoon-type systems include
(4)
seine nets, boom lift nets and others. In recovery arrangements, fish can
be harvested by draining the ponds and using dip nets, or by culturing in
cages. Other animals such as clams have been cultured in trays stacked in the
raceway on r
the raceway.
(4)
raceway on racks. Harvesting can be accomplished by lifting the rack from
The processing requirements of aquatic animals intended for human consumption
are not delineated here because current pulic health regulations prohibit this
practice when the water used in the culture of aquatic organisms is derived
from wastewater sources. Other processing steps that can be used involve
anaerobic digestion of fish to fertilizer products or protein supplements in
animal feeds as discussed previously in this chapter.
8-19
-------
REFERENCES
1. Henderson, S., "Utilization of Silver and Bighead Carp for Water
quality Improvement". In: Proceedings and Engineering Assessment,
Aquaculture Systems for Wastewater Treatment. EPA 430/9-80-006,
1979.
2. Site Visit. Reedy Creek Utilities Company, Walt Disney World, Orlando,
Florida. November, 1981.
3. Aquaculture Planning Program, Center for Science Policy and Technology
Assessment, "Aquaculture Development for Hawaii: Assessments and
Recommendations". Honolulu Department of Planning and Economic
Development, State of Hawaii, 1978.
4. Joint Subcommittee on Aquaculture, National Aquaculture
Development Plan, Draft 2, 1981.
5. Hephner, B. and G.L. Schroeder, "Wastewater Utilization in
Integrated Aquaculture and Agriculture Systems", Proceedings:
Wastewater Use in the Production of Food and Fiber, EPA
660/2-74-041, 1974.
6. Carpenter, R.L., H.K. Malone, A.F. Roy, A.L. Mitchum, H.E. Beauchamp
and M.S. Coleman, "The Evaluation of Microbial Pathogens in Sewage
and Sewage-Grown Fish", Proceedings: Wastewater Use in the
Production of Food and Fiber, EPA 660/2-74-041, 1974.
7. Goldman, J.C. and J.H. Ryther, "Waste Reclamation in an Integrated
Food Chain System", In: Biological Control of Water Pollution, J.
Tourbier and R.W. Pierson^Jr.,eds., University of Pennsylvania
Press, Philadelphia, PA, pp. 197-214 , 1976.
8. 21 U.S.C. sect. 346A.
9. Huguenin, J.E. and J.D.C. Little, "Marketing Issues Related to
Waste-Grown Aquatic Foods", Environmental Management, Vol. 1(5):
443-440, 1977.
10. Ryther, J.H., N.M. Dunstan, K.R. Tenore and J.E. Huguenin,
"Controlled Eutrophication - Increasing Food Production from the Sea
by Recycling Human Wastes", Bioscience 22(3): 144-152, 1972.
11. Bruhn, H.D., R.G. Koegel and D.F. Livermore, " Utilization of
Aquatic Vegetation", Paper presented at the Annual Meeting of the
North Atlantic Region-ASAE. Cornell University, Ithaca, NY, 1975.
8-20
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12. Robinson, A.C., H.J. Gorman, M.Hillman, W.T. Lawhon, D.L. Maase, and
T.A. McClure, "An Analysis of the Market Potential of Water
Hyacinths - Based Systems for Municipal Wastewater Treatment",
Batelle Columbus Laboratories, N76-28679, 1976.
13. Bagnall, L.O., T. deS. Furman, J.F. Hentges, Jr., W.J. Nolan and R.L.
Shirley, "Feed and Fiber from Effluent - Grown Water Hyacinth,"
Proceedings: Wastewater Use in the Production of Food and Fiber.
EPA 660/2-74-041, 1974.
14. National Academy of Sciences. Making Aquatic Weeds Useful: Some
Perspectives for Developing Countries, 1978.
15. Personal Communication. Bill Wolf, Necessary Trading Company, New
Castle, Virginia. November 18, 1981.
16. Personal Communication, Gary Crouch, Anderson Associates, Inc., New
Castle, Virginia. November 13, 1981.
17. Nolan, W.J. and D.W. Kirmse, "The Papermaking Properties of Water
Hyacinths", Hyacinth Control Journal 12, 1974.
18. Rudescue, L., "The Use of Sawgrass for Paper Product Manufacture:
An Examination of Properties", In: Biological Control of Water
Pollution, J. Tourbier and R.W. PiersonTJr., eds. University of
Pennsylvania Press, Philadelphia, PA. pp. 191-196, 1976.
19. Seidel, K. 1976. Macrophytes and Water Purification, In: Biological Control
of Water Pollution, J. Tourbier and R.W. Pierson, eds., University of
Pennsylvania Press, Philadelphia, pp. 109-121, 1976.
20. Wolverton, B.C., R.C. McDonald and J. Gordon. "Bioconversion of
Water Hyacinths into Methane Gas: Part 1. NASA Technical
Memorandum TM-X-72725 Bay St. Louis, Mississippi, 1975.
21. Benetnann, J.R. "Energy from Wastewater Aquaculture Systems", In
Proceedings and Engineering Assessment, Aquaculture Systems for
Wastewater Treatment, EPA 430/9-80-006, 1979.
22. Wolverton, B.C. and R.C. McDonald, "Energy from Vascular Plant
Wastewater Treatment Systems", Economic Botany 35(2): 224-232,
1981.
23. Colt, J. and M. Bender, "Economics, Energy and By-Product
Utilization", In: Proceedings and Engineering Assessment,
Aquaculture Systems for Wastewater Treatment, EPA 430/9-80-006,
1979.
24. Easley, J.F. and R.F. Shirley, "Nutrient Elements for Livestock in
Aquatic Plants11, Hyacinth Control Journal 12, 1974.
8-21
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25. Culley, D.D., Jr. and E.A. Epps, "Use of Duckweed for Waste
Treatment and Animal Feeds", Journal of the Water Pollution Control
Federation. 45(2): 1973.
26. Bakaitis, N.M. "Analysis of Sewage Lagoon Biomass Water Soluble
Vitamins by Microbiological Techniques", Proceedings: Wastewater
Use in the Production of Food and Fiber, EPA-660/2-74-041. pp.,
1974.
27. Lee, C. and T. McKim "Water Hyacinth Wastewater Treatment
System", Walt Disney World, Florida, undated.
28. Wolverton, B.C. and R.C. McDonald, "Water Hyacinth (Eichornia
crassipes) Productivity and Harvesting Studies", U.S. National
Aeronautics and Space Administration, ERL Report No. 171, Bay St.
Louis, MS, 1978.
29. Stewart, A. E., III. "Utilization of Water Hyacinths for Control in
Domestic Wastewater—Lakeland, Florida", In: Proceedings and
Engineering Assessment, Aquaculture Systems for Wastewater
Treatment, EPA 430/9-80-006, 1979.
30. Dinges, R. Natural Systems for Water Pollution Control, Van
NostrandReinhbld Environmental Engineering Series, Van Nostrand
Reinhold Company, New York., 1982.
31. Koegel, R.G., D.F. Livermore and H.D. Bruhn, "Aquatic Plant
Harvesting: Economic Technical and Management Aspects", Paper No.
74-5518, American Society of Agricultural Engineers, 1974.
32. Montgomery, W.D. and B.C. Wolverton, "Evaluation of Solar Dryer
for Drying Water Hyacinths", National Aeronatics and Space
Administration, NSTL, Bay St. Louis, Mississippi, 1976.
33. Site Visit. Plant City, Florida. November 6, 1981. Mr. B.L. Cartter,
Florida Department of Environmental Regulation.
34. Baldwin, J.A., Hentges, J.R. and Bagnall, L.O., "Preservation and
Cattle Acceptability of Water Hyacinth Sludge", Hyacinth Control
Journal, 12, 1974.
35. Suffern, J.S., C.M. Fitzgerald and A.T. Szluha, "Trace metal
concentrations in oxidation ponds", Journal of the Water Pollution
Control Federation 53: 1599-1607, 1981.
36. Personal Communication. Lowell Keup, U.S. Fish and Wildlife Service,
1982.
8-22
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