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Kansas State University
Research Collaborative for Aquaponics Technology System Design
Final Report
Victoria Eastman, Shannon Bellamy, Luke Alpers, Riley Arthur, Katelyn O’Brien
BAE 231
Dr. Lisa Wilken
13 December 2018
Table of Contents
Executive Summary…………………………………………………………………….…………Client needsDesign Goals, Principles and Constraints Description of DesignRecommendations, Limitations and Conclusions
Introduction and Justifications ……………..…………………………………………………...Objectives and Limitations…………………...………………………………………………….Background Research …………………………………………………………………………..
IntroductionGeneral Aquaponics
Background StandardsSystem Components Previous Solutions Potential Plant Option for Aquaponics SystemMaintenance
Background on NamibiaGeography Namibian ClimateFood CultureTechnology Available Restrictions and Regulations Cost
Conclusion Alternatives Considered………………………………………………………………………….
Design FeaturesFilter Components
Final Design Description…………………………………………………………………………General designDimensions and logisticsSystem ComponentsFishPlantsPathogen BiosensorImplementation of System in NamibiaAdvantages and DisadvantagesDesign Recommendations
Testing Needs …………………………………………………………………………………….Summary ………………………………………………………………………………………..References………………………………………………………………………………………...
Executive Summary
Client Needs
It was requested that the team design an aquaponic system, which is an integrated aquaculture
(fish farming) and hydroponic system (the production of plants in water without soil) equipped with a
pathogen (E. coli) biosensor for a Gästefarm in Namibia. Aquaponics systems are composed of
aquaculture (fish farming) and hydroponics (the production of plants in water without soil), which
provides a more sustainable and cost-effective way to produce food. The design team must ensure that the
system produces enough vegetation to assist in feeding the sheep and diversify farming practices.
The design team must take into consideration that there are restrictions on what types of fish and
plants can be used for the aquaponics system. The design must also be low in cost and easily maintainable
to ensure sustainability.
Design Goals & Principles and Constraints
The objective of this design was to develop a food production system capable of feeding a small
subsistence farmer’s herd of 25 sheep and provide a supplementary protein source for the community. In
the process of designing a food production system RCAT adapted principles from a conventional
aquaponics system to fit the needs of the client.
Within the objective were a few imperative constraints. The client required the system to feed 25
sheep continuously. RCAT also identified that it would be important for the system to require little
maintenance and labor. Though the farmer will be experienced in farming operations, aquaponics systems
can be complex and may require some special knowledge to operate. RCAT proposed a simplified, yet
effective, design because of the customer's inexperience with aquaponics systems and the design was
simplified, but runs just as effectively. RCAT’s simple design means the cost for the system is much less
than conventional aquaponics systems. Lastly, the client requested there be an E-coli sensor integrated
into the water circulation system to test water quality along with a filtration system. This would allow for
a sustainable enclosed environment while monitoring the health of the aquaponics system as a whole.
Description of the design The Research Collaborative for Aquaponic Technology (RCAT) Design is a collapsible cubic
plant-above water design which consists of one tank for plants and growing media, offset on top of a
larger water fish tank below. The main tank is a 5 ft x 5 ft x 5 ft cube made of polyethylene terephthalate
(PET) fish and water, with another 1.25 ft x 5 ft x 5 ft offset top to hold the growing media and produce.
A single pipe, attached to a pump connects the water tank to the plant box and transports the water from
tank to plants. The base of the plant bed is slightly slanted and will contain several evenly-spaced small
holes with a radius of 1in to allow water to drain from the plant bed back into the fish tank. The growing
media used in the plant bed is soil, rocks, and pebbles small enough to not fall through drainage pores.
Finally, a PET pipe with radius 0.30 ft will be connecting the two systems with a 250 gal/h Hydrofarm
Active Aqua AAPW250 Submersible Water Pump to pull the water from the tank into the growing bed.
The fish selected are Nile Tilapia (Oreochromis niloticus) which are very disease resistant, spawn
quickly and can be found locally in Africa. While the system can support a variety of crops, the ideal
produce selected to grow in this system will be the cowpea (Vigna unguicalata) which are resilient
legumes that serve as a staple in Namibia, where their seeds can be locally sourced. In addition, this
system will also include a disposable, cost-effective, simple biosensor which is capable of detecting
Salmonella typhimurium, and Escherichia coli strains JM109 and DH5-α.
Recommendations, Limitations, and Conclusions
The Research Collaborative for Aquaponic Technology (RCAT) team recommends this small,
simplistic design to demonstrate feasibility. The small design also eases the labor of construction as well
as ease of transportation. The recommended fish are Nile tilapia, native to Africa, and the plants grown
will be cowpeas. All the components of the system are kept in close proximity to ease the flow of the
system and make it simpler to construct. Additionally, the symbiotic relationship between the plants and
fish are easier to maintain and observe.
The system can independently function on its own, with the exception of a source of food for the
fish, which will need to be provided by an outside source. The small-scale structure limits the produce of
the fish and plant, but the design can be replicated to increase the potential yield. Water flow is controlled
to an extent, but there could be enough stagnant water in the fish tank that the ammonia and nitrate levels
could affect the fish. Overall, the final design meets all the criteria the client is looking for, while also
providing room to grow.
Introduction and Justifications
A farmer in Namibia requested a small-scale aquaponics system to implement on his farm that
would aid in feeding a small herd of sheep as well as providing a food source, from the fish, for the
farmer and his family. Aquaponics systems are a symbiotic relationship between aquaculture (fish
farming) and hydroponics (growing plants in water without soil), which is a more sustainable way to
produce food. The client wants a simple system that is cost effective, simple in design and requires low
every day maintenance. The RCAT team was tasked with designing a system that met all the client’s
requirements.
Design Objectives and Limitations
In order to create a design that met all of the client’s needs, RCAT had to first identify all
the possible design constraints. The most important constraint the client specified was the need
for a simplistic, easy to use design that requires minimal maintenance. Because this is the
farmer’s first experience with aquaponic systems, RCAT wanted the design to be as
straightforward and easy to use as possible. The next main constraint was the need for a
biosensor capable of detecting E. Coli to ensure health and safety associated with the system.
Another key constraint was that the farmer wanted the design to incorporate produce and fish
food that was readily accessible, familiar, and complied with all fish restrictions in Namibia.
Finally, the last constraint RCAT was focused on was that the design needs to effective, with the
ability to produce a sustainable, reliable yield within the harsh Namibian climate.
Background Research:
Introduction:
Aquaponics systems play a big role in finding a more efficient and sustainable way to
produce food. They are a beneficial way for people, especially those in more under-developed
countries like Namibia, to grow food conservatively. To design one of these self-sustainable, low
maintenance systems, one must first understand what exactly an aquaponics system is, what
components are needed, and what fish and plants can be used. When designing for another
country like Namibia, one also has to account for the culture, restrictions and regulations,
climate, and geography of the country.
General Aquaponics:
Background
To fully understand the project, a basic understanding of aquaponic fundamentals and
standards is essential. Aquaponics is a combination of aquaculture and hydroponics. It consists
of a body of water, like a pond, containing fish or other aquatic animals and plants. Image 1
(below) shows the flow and basic functions of a typical aquaponics system.
The water in the fish tank contains nutrients and waste from the fish that help the plants
grow. Aquaponics systems are an ideal solution for making food production sustainable,
especially in developing urban countries (Goddek et al., 2015). Aquaculture and hydroponics
have a symbiotic relationship in this single system, this allows for less maintenance as the water
does not need to be replaced because of excess nutrients (Goddek et al., 2015).
Aquaponics cycle (Small Garden
Ideas, 2016)
Image 1. Aquaponics cycle (Small Garden Ideas, 2016)
In aquaculture, which is also known as aquafarming, fish are raised in a controlled
environment. A caveat of aquaculture is that ammonia from fish waste can end up killing the
fish, so the water has to be tended regularly. In hydroponics, plants grow in water that has
nutrients added. In aquaponics, the fish waste is used as food for the plants which resembles the
nature in lakes and ponds. Aquaponics systems are not only a sufficient way to grow food, but
they also conserve water, so water is only lost through evaporation and transpiration, thus being
a sustainable solution to food production (Marklin et al., 2013).
Standards
Understanding the current aquaponics standards are essential to developing a design
capable of performing essential functions in the field. The current industry standard for grow
beds are at least 12 inches deep and must be made out of food safe materials that do not alter pH
(Bernstein and Lennard, 2018). In addition, systems that contain upwards of 250 gal of water for
the fish tanks tend to be the most successful as they allow room for error as impacts take longer
to see at larger volumes. The standard for fish-to-water ratio is one fish for every five to ten
gallons of water. Similarly, the standard for grow beds is one fish for every one square foot of
grow bed surface (Bernstein and Lennard, 2018).
System Components
Having researched the basic backgrounds and standards regarding aquaponic systems, the
next step in preparing a design is to consider the more specific system components such as power
sources, filtration systems, pumps, biosensors and maintenance. The first component researched
was the potential power sources for the system, as determining a powersource is one of the first
steps when considering a design. Solar power is one of the cleanest forms of renewable energy,
but also one of the most expensive (Grimes, 2011). However, as solar panels are becoming more
prevalent, the demand is increasing so the prices are decreasing. One drawback to using solar
power is the need for an inverter to convert the electricity from DC to AC. Water pumps and air
pumps used in aquaponics systems require AC power. All components necessary to operate an
aquaponics system include a solar panel, voltage regulator, battery, microcontroller and relay,
and DC step up inverter. The power collected by the solar panel is stored in the battery and the
microcontroller and relay determine where the power goes(Murmson, 2018). It can determine
when the water pump needs to turn on or the air pump can turn off to make the best use of
energy in the system. During the nighttime hours, the battery supplies all necessary power to
keep the system functioning until the sun returns.
Each solar panel is built on a frame of any material and rotates on a pivot to capture the
maximum amount of sun possible in a day. The rotation is determined by a microcontroller
which communicates with other electrical sensors in the system to determine the most efficient
orientation of the solar panels. These sensors include thermocouples, photoresistors, and
thermistors. Rotation of the panels is caused by the actuation of servo motors, linear actuators,
and solenoids. This design of solar panel is usually attached to a fixed structure such as a
greenhouse or building with multiple solar panels working in sequence. The fixed structure
allows the pivot point to be secured to the frame of the building (Hall et al., 2010).
Having considered the power source, the next key component of an aquaponics system to
focus on would be the filtration and pump systems. To begin with, there needs to be two
filtration systems, one for solid particles and one for nitrification. A biofilter is needed so that the
toxins from ammonia in fish urine and excretion of the gills do not affect the plants which could
harm the people that consume said plants. Water flows through the fish pond into a biofilter
which consists of nitroso-bacteria and nitro-bacteria that can break down ammonia. This way the
ammonia can be converted into nitrite, then into nitrate. Nitrate is less harmful to the fish and
serves as the main nitrogen source for the plants (Goddek et al., 2015).
Biofilters typically contain nitrifying bacteria that grow attached to a submerged surface
or in a water column. The bacteria takes the ammonia from the water and oxidizes it into nitrate
automatically reducing the need for maintenance and another external filter. In order for the
majority of the ammonia in the pond to be broken down, the filter has to be fairly large since the
pond itself is large. Recommended components of a biofilter are sand, crushed rock, river gravel,
or plastic shaped into small beads. Biofilters must be non-degradable and long-lasting so less
maintenance is required (Ebeling, n.d).
In addition to filters and pumps, this project also requires a biosensor capable of detecting
harmful E. Coli in the system. Likewise, installing a pathogen biosensor to detect any harmful
bacteria within in the aquaponic system is crucial for the well-being of those who will be
consuming the products of the system. Harmful pathogens such as Escherichia coli can cause
many health issues, such as diarrhea, urinary tract infections, respiratory issues and more (Lui,
2007). Damaging E. Coli bacteria can develop and mature in raw vegetables due to contaminated
water from runoff of animal farms (Lui, 2007).
A disposable biosensor that can detection pathogens is ideal for an aquaponic system.
The biosensor within this system must be as simple to use as possible for the Namibian farmers
using it. One sensor, developed by Ali et al. (2018), provides a reading and classification of
Salmonella typhimurium, and the Escherichia coli strains JM109 and DH5-α within only 8 min
after the injection (Ali, 2018). This biosensor is has a small strip like shape. The sample that is in
need of analysis is then injected onto the strip with probes connecting to an impedance analyzer
and computer providing an accurate reading within a short period of time (Ali et al. 2018).
Previous Solutions
In addition to understanding the basics of aquaponics, it is also essential to consider the
design of the system. This is best done by evaluating the current project requirements and
comparing them to current designs and standards. For this project, the farmer wants the design to
be simple and efficient. One example of a successful design is big greenhouses stocked with
different plants for diversity and pools with the fish are made out of concrete (Agribusiness TV
(n.d.)). Applying his methods on a smaller scale could be an option, but his options are a little
pricey. Some of the materials he uses are items he has transformed from their everyday purpose
to use, which could be an option. He has cut pipes to form hanging garden plants that are watered
by the filter system that comes from the fish. He also uses bioenergy as well as solar energy, so
the greenhouse is running night and day which could be considered as well.
Another design option is to use giant bins or again a concrete structure that could use
gravity (weir gravity flow) and sloping bottoms to also help with cleaning (Wicoff, 2011).
Instead of a system where the water is pumped to the plants, the plants could be grown in netting
or on a sturdy surface with holes that is set on open pipes, so the plants could soak up the
nutrients while the water is circulating. This would allow less space to be taken up by rows of
vegetation, but it could also limit the amount of vegetation (Wicoff, 2011).
Potential Plant Options for Aquaponics Systems
While considering the design structure of the aquaponics system, it is also important to
determine which produce should be used. For example, in a recirculating aquaponics system, it is
imperative to stock plants that can efficiently remove inorganic nitrogen and phosphorous from
the water. Water spinach (Ipomoea aquatica) was observed to reduce the total ammonia
nitrogen, nitrite-N, nitrate-N and orthophosphate with efficiencies of 78.32–85.48%, 82.93–
92.22%, 79.17–87.10%, and 75.36–84.94% (Enduta et al., 2012). In this experiment, water
spinach exhibited qualities in its root system which harbored superior populations of microbial
life. The surface area of the root system not only improved microbe populations, it allowed for
more water pollutants to be taken up by the plant (Enduta et al., 2012).
Leafy greens are generally grown in aquaponics system because they are easy to grow,
and they are in high demand. Small roots and shoots can be grown in an aquaponic system and in
fact grow faster than leafy greens. In an aquaponic environment, they should be harvested prior
to being fully grown. Harvesting roots like turnips, radishes, and carrots in their earlier stages in
growth makes them softer, sweeter, and more desirable to consumers (Kozai et al., 2016). Leafy
greens and herbs are grown more prevalently in aquaponics systems in urban areas because they
can be harvested and consumed without any extra processing (Kozai et al., 2016). No pesticides
are used in aquaponics systems, so when the leafy greens are harvested there is no need to wash
them prior to serving.
A few examples of leafy greens which are indigenous to Namibia include Amaranthus,
Corchorus and cleome (Araya, 2014). Below is a list of several commonly found edible plants in
Namibia. They have high levels of calcium, iron, vitamins A and C, and are rich in protein and
fiber (Araya, 2014). Plants like Amaranthus and Corchorus are considered low management
crops because of their ability to grow in low quality soil. In an aquaponic application where the
nutrients found in soil are highly concentrated, it is possible that the yields may increase. Many
of these indigenous species have not been studied for cultivation since they are simply wild
vegetation. However, they could prove to be useful in a cultivation-type environment due to their
extreme drought tolerance and ability to grow in poor soil.
Indigenous Plant Species to Namibia (Araya, 2014):
● Amaranthus retroflexus (Pigweed)
● Cleome gynandra (Spider Plant)
● Corchorus spp (Gushe)
● Brasica carinata (Kale)
● Solanum retroflexum (Nightshade)
● Cucurbuta spp (traditional pumpkin)
● Citrallus lanatus (Bitter melon)
● Vigna unguicalata (cowpea)
● Colocasia esculenta (Amadumbe)
Maintenance
Having evaluated the main components of an aquaponics system, the next main area of
focus would be on maintenance. A healthy ecological balance in an aquaponics system starts
with a well-maintained system. The primary waste product that collects in an aquaponics system
is solid waste produced by the chosen aquatic animal species. This solid waste can be dealt with
in two ways; recycling the waste back into the system or removing it from the system
(Bodlovich, Gleeson, 2006). A partially closed-circuit aquaponics system would recycle a
majority of the waste back through the system (Bodlovich, Gleeson, 2006). The waste is taken
into a bio-waste digestion unit allowing the waste to degrade within the system and eventually be
used by the plants in the system. Keeping the waste in the system means minimal water is
expelled thus the system requires minimal water to be added (Bodlovich, Gleeson, 2006).
The second method of dealing with solid waste is to remove it from the system entirely.
This can be accomplished by filtering or separating the solid waste from the water (Bodlovich,
Gleeson, 2006). When removing solid waste from the system it is preferred to use a filtration
system using any appropriate media filter. A second option is the swirl separator. Solids are
settled in a waste stream and removed from the system while smaller particles would still have to
be filtered out by a media filter as previously described.
A thorough yearly cleaning is necessary to keep an aquaponics system functioning at its
highest capacity (Martell, 2016). Generally, this cleaning takes place in the spring when plant
varieties are being rotated. Solid waste removal is the first priority during the yearly cleaning
process. Place a pump in the bottom of the tank and remove one third of the water from the tank.
This water can be then applied to other plants or vegetation as a fertilizer. After the water is
drained refill the tank with dechlorinated water. Calcium and potassium deposits will form on all
exposed parts of an aquaponics system including plumbing components. These deposits can be
removed by scrubbing with a clean towel and low concentration phosphoric acid.
Background Information on Namibia:
In order to more fully understand the location in which this system would be utilized, a
general understanding of Namibia is needed. In this section, Namibia's food culture, climate,
town layout and available technology are all evaluated, beginning with the most relevant topic,
Namibian food culture.
Geography
With a detailed understanding of the climate around the farm, it is then important to learn
more about the layout of the country in general in order to more fully understand the area in
which the design is to be implemented. For example, Namibia is roughly 824,000 km2. It is
mostly desert and water is limited. Even the rivers are dry, except during the rainy months. It is
made up of four main geographical sections, the Namib Desert which consists of sand dunes and
gravel fields, a mountain that resembles a wall, the Central Plateau which is where most of the
population is, and the Kalahari Desert which consists of sand dunes and little vegetation
(Namibia Travel, 2010). Even though it does not rain throughout the year, there are underground
water reservoirs because of layers of clay and rock which supply water to the farms (Namibia
Travel, 2010).
Looking at a map of Namibia (image 2), Helmeringhausen is located in the south
western part of Namibia, just on the edge of the mountain wall and the central plateau (Expert
Africa, 2016).
Image 2. A map of Namibia (Expert Africa, 2016)
Namibian Climate
Although an aquaponic system is capable of producing plants and aquatic life forms
without the use of soil and natural rainfall, the climate and weather of whatever region where the
system is located still plays a significant role in which plants and animals can be used within the
system. The Southern African country of Namibia has a very arid climate meaning as the rate of
evaporation is much higher than the rate of precipitation (Singh, 2018). Namibia has an average
of 300 days each year of sunshine (Singh, 2018). This excessive amount of sunlight creates a
design constraints on which plants can be farmed within the aquaponic system and the overall
design of the system. Plants that cannot survive with full sunlight must be shaded in some way,
so a plant that can tolerate full sunlight may thrive within this system.
In the town of Helmeringhausen, where this aquaponics system will be located, the
average annual precipitation is 203 mm (Mountney, 1999). Combined with an average summer
high of 90°F (Mountney, 1999), water is not readily available or accessible in this town. Finding
a regular source of water capable of being pumped into the system is a very important factor in
having successful food output. Namibia’s climate is harsh, but that is why there is a need for an
aquaponics system.
Food Culture
To determine which produce should be utilized in an aquaponics system, a general
understanding of the cultures cuisine is needed. Namibian cuisine culture is centered around
traditional cooking methods, with most dishes having German and South African influences
(Gale, 2001). In addition, most of the Namibian cuisine is centered around beef and fish, as cattle
farming and fishing are two of the main agricultural productions. Some common dishes include
Kapana (raw beef cooked on an open flame), Kabeljou (Silver Cob) and Luderitz crayfish (Gale,
2001).
A good understanding of the meal culture is also essential to planning a successful
aquaponics system. Many Namibians eat only one to two meals a day, and as a result, need very
protein-rich, high carb meals. They find these protein and carbs in vegetables and meat sources.
Pap (maize meal porridge), beef and fish being three of their primary staples (Shusko 2015). The
type of foods they eat depends heavily on their location in the country, as it is such a culturally
diverse area. Those in the Kavango and Zambezi regions consume fish frequently and would
therefore benefit the most from an aquaponics system (Shusko, 2015).
Having gained a thorough understanding of the Namibian food culture in terms of
aquaponic systems, it is then necessary to consider the weather and climate in order to design an
effective food-producing system.
Technology Available
With a basic understanding of the culture and layout of the country, the next main
component that needs to be evaluated is the available technology. A knowledge of the
availability of technology in the host country is essential when designing such a system. That
being said, the aquaponics system being designed for farmers of Namibia is going to be equipped
with a pathogen biosensor, so the technological advancements of the country are an important
thing to consider when designing the system. Namibia is slowly but surely moving towards a
technologically advanced country. Coding is in-fact being integrated into the nationwide school
curriculum of Namibia (Matengu, 2016). Although late to the game, Namibia as a whole realizes
that the future is technology, so they have made large efforts to keep up with the ever growing
cyber world we know today (Matengu, 2016). There should be very few issues with the
Namibian people capable of using and reading a pathogen biosensor fixated within an
aquaponics system.
Since Namibia became an independent country in 1990, mining has been largest
contributor to the economy of the country (Kiangi, 1997). Being the world leader in diamond
mining, Namibia has made substantial technological advancements in machinery and over all
technique and extraction of diamonds. Fresh of gaining independence in 1990, the mining
industry created the Namibian Institute of Mining and Technology (NIMT) (Kiangi, 1997).
Education and technology are of the utmost importance to the Namibian government and people.
Finally, having taken the country’s culture and technology into consideration, the final
component that needs to be discussed is the availability of resources at the exact location the
system is to be implemented into. To begin, the resources available at the site of interest are two
reservoirs about a 15 minute drive apart from each other, that could be used as a water supply.
The farmers have also already implemented solar panels that could provide electricity if needed
to the aquaponic site as well as a small generator. The aquaponic system will need to feed all the
sheep on the farm, since the farm is located next to a desert and mountain area and plant life is
not overly abundant (Cline, 2018). While there is nothing already set up in the location, the
farmer is willing to invest in building a system.
To make the benefit worth the cost, the aquaponic system will need to be cost efficient to
build and maintain. Starting on a smaller scale may be the best option to start with then
expanding on the business. Right now, the primary need is to feed the sheep and fish, and the
sheep are easier to feed for, since the sheep also eat the vegetation on the land. The fish,
however, will completely need their own food from the aquaponics system, since fish food is
pricey (Cline, 2018). Seed for the sheep food should be cheap; however, fish food could be
tricky to grow based on the fish picked. Location will also be essential. There are two reservoirs
and there is the option to use both or only one to begin with. To be safe, using one simple and
smaller design may be smarter than trying to make a giant aquaponics system that could be
costly and not effective.
Restrictions and Regulations
Careful consideration of restrictions and regulations is needed to design a safe, effective
aquaponics system. In addition to the basic fish and plant set-ups, there are also essential
standards for filtration and resource cycling as well. The ideal standard for water flow is moving
the entire volume of the fish tank through the grow beds every hour using a 15 min on, 45 min
off system. Fishless cycling is also recommended because it allows for the buildup of bacteria in
the tank which will later result in faster fish stocking. A test kit should be used to measure
ammonia, nitrate, nitrite and pH, ensuring that ammonia and nitrite levels are always under 0.75
ppm. In addition, aeration devices are also recommended for adequate oxygen levels (Bernstein
and Lennard, 2018). All of these aquaponics standards should be taken into consideration when
designing a model.
In addition the general restrictions and standards, understanding the current Namibian
laws that pertain to aquaculture is also important when considering a design specified for this
country. In 2002, Namibia founded the Aquaculture Act which is managed by the Ministry of
Fisheries for the overall purpose of promoting sustainable aquaculture and manage and
protecting marine and inland aquatic ecosystems (Leicht and Gerhardt, 2014). This is the main
legal guidelines for any aquaculture-related topic such as health management, disease control,
environmental protection and access to land and water. One key regulation outlined in this text
includes the requirement of a license, which is granted by the Ministry of Fisheries to anyone
who has obtained the proper paperwork and who has designed an acceptable system in the eyes
of said Ministry. This includes designing a system that has water-access and an acceptable
method of wastewater disposal. In addition, it the Ministry of Fisheries will oversee all license
holders’ practices to ensure there is no accidental or intentional release of alien species, nor the
spread of harmful diseases. All aquaponics systems and license holders must keep detailed
records to be subjected to viewing by the Ministry at any given time (Leicht and Gerhardt, 2014).
In addition to knowing the regulations and restrictions, in order to implement an effective
Aquaponics system, it is also important to understand the availability of agriculture and fishing
in the area. Namibia, or the Republic of Namibia is a largely arid desert country on the
southwestern coast of Africa (Green, 2018). Despite being a coastal country with five permanent
rivers, the sharp reefs and impassable rivers makes it difficult for residents to obtain imported
goods. Similarly, the barren sandy and rocky soils that span across much of the country make
farming difficult. These agricultural issues stem not only from the lack of fertile soil, but from
the water availability in the more arid desert regions. In addition, fishing in Namibia is limited by
stock levels, which have increased significantly with recent conservation attempts (Green, 2018).
These factors should both be taken into consideration for designing an aquaponics system.
Since the aquaponics system in question requires local fish food, understanding the
availability of fish in Namibia is essential to consider when determining stock. Currently,
offshore boating and rock-and-fish angling are common techniques to catch Snoek, Steenbras,
Galjoen, Kabeljou, Blacktail and other well-sought after fish. These fishing techniques are all
strictly monitored by the Namibian sport-fishing industry and the Ministry of Fisheries and
Marine Resources (MFMR) that restricts how much of which fish can be caught and farmed at a
time (Jacobi, 2011). The goal in this effort is to conserve dwindling stock. When transporting
fish to the farm site, the most relevant regulation is the maximum of 30 fish which may be
transported in a vehicle at a time per fisherman (Jacobi, 2011).
Cost:
Having gained insight on general aquaponic system components and the country of
Namibia, another component to consider is cost and the amount the customer is willing to pay..
The items potentially needed for constructing an aquaponics farm are: lumber, pipe, fish tank,
greenhouse, and filters to keep the system sanitary according to Portable Farms (Davis, and
Davis, 2018). The materials for the final aquaponics design will be mostly made of plastic, (pipes
and tank) or recycled materials to keep the design cost effective. Most of the price for the system
will come from the biosensor and the filtering components.
Shipping items out of the country could be an option for materials if the cost remains
cheap enough, however, the farmer would like the most affordable plan. The only item that
might need to be potentially shipped is either the biosensor or fish, but domestic fish and plants
is the best option. Another important component to consider the durability of the materials long-
term. Maintaining a low cost while also ensuring the long-term sustainability of the aquaponics
system will be taken into consideration for the design.
Conclusion:
In conclusion, it is incredibly beneficial to find more sustainable ways to produce food.
Aquaponic systems are an efficient way to help people in underdeveloped countries, like
Namibia, grow food conservatively. These systems are a more efficient way of conserving
limited resources, like water and space, while also maximizing produce. In order to design the
most effective system, it is important to understand what an aquaponics system is, what
components are needed, what fish and plants can be used, and also the culture, restrictions and
regulations, climate, and geography of the country.
Alternatives Considered
Design FeaturesThe RCAT design team focused on a wheel design, evaporative cooling, plants on top of
the fish tank, below ground tank, and retractable awning as our design features to be compared in
the decision matrix. As a group, it was decided that all aquaponics have the same basic design.
Rather than re-inventing the entire system, RCAT focused on individual components which
could improve the efficiency of the system.
The wheel design is an alternative plant growing structure where the plants are situated
on racks fixed between two wheels. As the wheels spin, the racks will individually pass through
the water to collect water and nutrients from the fish tank. The evaporative cooling system is
based on ancient terracotta air cooling systems. Water passes vertically through a cluster of
horizontally oriented terracotta tubes. As air passes through the tube cluster water vapor cools
the air. This design was thought to be more applicable to cooling the water and sheep. Placing
the plants on top of the fish tank simply removes a growing bed from beside the fish tank and
places it on top of the tank instead. The team also considered installing the tank below ground.
All parts of the aquaponics system would remain the same as they would above ground except
that they would be below ground. The last design feature to be considered was installing a
retractable awning above the entire system. This would provide shade to the plants and fish
during the day.
For the project’s specific objectives and constraints, the team selected cost, most effective
method of growing plants, how the overall design would affect the stress levels of the fish,
maintenance, design simplicity, and overall “coolness” of the design. The system should be
within a reasonable and preferably low cost and also be able to produce a fair amount of plants to
sustain the herd of sheep while maintaining the fish, stress-wise and population-wise. The need
for maintenance everyday should also be low. In addition, some designs have more complex
components that may break, which also falls into the simplicity factor of the design. The
aesthetics also varies with each design. For example, consider the wheel design. This design was
ranked as having the highest coolness factor because it simply would be the coolest design.
Every component was put on a 1-10 scale with 1 being low and 10 being the highest. That
number is then multiplied by the importance factor of that component of the design and then all
the numbers are added together to get the final total number for that component for that design.
All the numbers are then compared with the highest total number being the best option on paper.
Using these criteria, the team determined the best overall design was the plants directly
on top of the fish tank design. The team agrees with the results of this decision matrix. This is the
cheapest, simplest, most effective system that will be most readily implemented at the Namibia
site. While that will be the basis of our system, the team also plans to add a couple features to
enhance the simplistic design. The team is still discussing how the plants will be positioned
above the tank, in what way the plants will be stationed there, and how the filtration will be
implemented.
Filter Components
The alternatives selected for filtering the aquaponics system are bottom feeders as water
filters, fish as water filters, manually removing solid waste, plants as water filters, an electric
pump filter, and bacteria filters. Bottom feeders and fish were considered to be incorporated into
the aquaponics system as a filtering system because there is not much cost and would eliminate
the need or a mechanical filter or at least aid in the filtration process. Manually removing solid
waste is another very cost-effective option to filter the water, because the only action needed is
hosing out the tank occasionally. Using plants as filters to clean the water does not negatively
affect the fish within the system in any way. An electric pump filter is highly recommended
because it is a very effective and easy way to keep the water clean. Bacteria filtering the water is
the final potential filter option, because there is essentially no cost, no impact on fish life, and is
very accessible.
For filtration system constraints for the aquaponic system, cost, filtration efficiency, accessibility
of material, maintenance requirements, impacts on fish and overall durability were compared.
These constraints were compared because they are all key aspects to consider when determining
an appropriate filtration system. Using these constraints and a general knowledge of our
Namibian location, the team determined that an ideal filtration system would incorporate easily
accessible parts and be cheap, efficient, durable, non-disturbing to the fish, and would require
very little maintenance.
Using these criteria, all of the alternatives were evaluated and the bacterial filtration
system was determined to be the best filtration system . RCAT did not agree with the results of
this decision. While the team does agree that this system is the cheapest, simplest and most
readily available system, the team does not believe that it will be the most effective overall.
Instead, second-place winner of the decision matrix is the better option which was the bottom
feeder filtration system. This system is simple, has a reasonable cost, and will be the most
effective system overall. It is likely that these systems used in combination would be the
cheapest, most effective filtration system overall.
Final Design description
General design
The RCAT design team designed an aquaponic system for a client located at a small
Namibian farm. Figure 1 below shows multiple 3D views of the general design of the
aquaponics system. This is a simplistic plant-on-water design which consists of one tank for
plants and growing media, (fig. 1B), offset on top of a larger water fish tank below (fig. 1A). A
single pipe, (fig. 1C) attached to a pump connects the water tank to the plant box and
transports the water from tank to plants. Additional system components include a biosensor,
Cowpeas and Tilapia which are outlined in detail below.
Figure 1. RCAT Aquaponics 3D design including: A) fish tank, B) plants with growing media, and C)
water flow pipe.
Dimensions & Logistics:
The main tank seen fig. 1A will be a collapsible 5 ft x 5 ft x 5 ft tank made of
Polyethylene Terephthalate (PET) for fish and water, with another 1.25 ft x 5 ft x 5 ft offset top,
part B, to hold the growing media and produce. The base of the plant bed is slightly slanted and
will contain several evenly-spaced small holes with radiuses of 1 in to allow water to drain from
the plant bed back into the fish tank. The growing media used in the plant bed will be soil, rocks,
and 1.25 in pebbles that are large enough to not fall through drainage pores. Finally, a PET
pipe, fig. 1C, with radius 0.30 ft will connect the two systems with a 250 gal/h Hydrofarm Active
Aqua AAPW250 Submersible Water Pump to pull the water from the tank into the growing bed.
System Components:
As seen in Fig 2, fish in the water tank eat and then excrete ammonia while naturally
occuring bacteria within the system convert ammonia to nitrate. This nitrate-rich water is
pumped from the fish tank into the plant bed through the pipe. The water and nitrate is absorbed
by the plants, helping support healthy plant growth. Water not absorbed by the plants is filtered
through the plant growth medium which consists of a layer of soil on top of a bed of rocks and
pebbles. The slanted plant bed combined with small holes in the base of the plant bed allows for
excess water to drain back into the fish tank. The water is then pumped from the fish tank into
the plant bed again, repeating the cycle. The design team selected components (plants, fish,
and pathogen biosensors) most suitable to the design needs and constraints are highlighted
below.
Figure 2. Flow of Aquaponics system components (RPBAOnline, 2016)
Fish:
Tilapia, shown in Figure 3, is an industry standard for aquaculture and
aquaponics systems around the world (Aquaponics USA, 2017). They are native to the
Nile river basin in lower Egypt as well as other parts of Africa (Jauregui). A local, native
stock of fish would be more cost-effective and accessible. The Nile and Mozambique
are the two subspecies of tilapia that are farmed throughout the continent of Africa.
These two types of tilapia mature at a fast rate (Aquaponics USA, 2017). Female tilapia
spawn every 4-6 weeks, and the fertilized eggs are held in the mother’s mouth for 4-8
days. After the eggs hatch, the mother will continue to hold the “fry” in her mouth for
another 3-5 days. Tilapia is referred to as a “beginner fish” because they are extremely
resistant to disease and drastic temperature changes in the water.
All variables pertaining to the fish are determined by the stocking density of the
fish tank. The determined harvest weight for this system is about 1.5 pounds. The fish
will be stocked at a density of .25 pounds per gallon which would be 155 total fish in the
tank. The feed rate should be between 1.0 - 1.5 percent of the harvest weight (DeLong
et al., 2017) which would amount to 10g of food per fish every day. The tank will be fed
a total of 1550g of food per day. This population of fish will be more than enough to
sustain a single family. The purpose of such a substantial starting population is to allow
the fish to breed freely without human consumption stressing population. There will
always be a large enough population that the client will be able to consume freely within
reason. Tilapia will breed at a rate of 2 females for every male although some
commercial systems operate at up to 5 females per male. Each female will lay about 10
eggs depending on the size and age of the female (Towers, 2005). From the time the
eggs hatch until they are at harvest weight, which is between 10 and 12 months.
Figure 3. An adult tilapia ready for harvest. (EatPress, 2009)
Plants:
The plant chosen to grow in the proposed aquaponics system is the cowpea (Vigna
unguicalata) as seen in figure 4. Cowpeas are currently prevalently grown and cultivated
throughout the African continent (Gomez, 2004), so seed will be easily sourced within Namibia.
Cowpeas have superior drought resistance as compared to most other beans and perform best
in sandy soils (Davis et. al, 1991) making it the most fitting choice for Namibia.
Figure 4. Mature cowpeas (AgriFarming, ND)
Without knowing the species of sheep being farmed in Namibia it is difficult to know
exactly how much feed is necessary to provide to the herd. Assuming in the herd of 25 sheep
each sheep weighs about 150 pounds at full maturity each sheep would need to consume about
2.6 pounds of dry matter per day (Schoenian, 2018). In total, the herd of sheep will need 65
pounds of dry matter per day. Cowpeas have a much higher nutrient density as compared to
traditional livestock feed. One cup of cowpeas contains 13.22g of protein (HealthBenefits, 2018)
whereas one cup of alfalfa only contains 1.32g per cup (HealthBenefits, 2018). Therefore, a
smaller quantity of dry matter will need to be fed to keep the sheep at their desired growth rate.
Cowpeas can be used in every stage of growth (Davis et. Al. 1991). In many areas of the
world, the cowpea is the only available high-quality legume hay for livestock feed. Digestibility
and yield of certain species are comparable to alfalfa (Davis et. Al. 1991). Cowpeas are not only
beneficial to the animals they are feeding, but they are also beneficial for human consumption.
The International Livestock Research Institute (ILRI) identified cowpeas as a superior crop to be
cultivated for animal and human consumption (Kristjanson et. Al. 2002).
Cowpeas are not only beneficial for plant and animal consumption, but they would also
be easily integrated into Namibian culture. Cowpeas originated in West Africa and have been
cultivated by subsistence farmers there ever since (Abberton 2018). Cowpeas are a crop that
Namibian farmers would be familiar with growing and could integrate it into their production
systems. As a result, farmers would be more likely to accept cowpeas as opposed to a plant
that they were not familiar with growing, and the integration of the aquaponics system would be
more successful.
In RCAT’s designed system, not enough cowpeas are produced to fully sustain a herd of
25 sheep. The team believes that, though plant production falls short, the proposed system will
be the foundation on which more growing beds can be added and more cowpeas can be
produced. During further research and development RCAT is optimistic that the tank system
could support many more growing beds to expand the farmer’s production capabilities.
Pathogen Biosensor:
Figure 5. Schematic diagram of bacteria
Figure 6. (a) Comb type electrodes on a PET measurement and classification (Ali, 2018).substrate, the zoomed image shows Ag
nanowires in the space between two electrodes.
(b) Bacteria engaged with sensor that
varies the impedance of
the sensor (Ali, 2018).
Lastly, the design includes a biosensor for detecting Escherichia coli to ensure
that any pathogen breakouts within the aquaponics system can be dealt with before any
damage is caused. The biosensor used with this aquaponics system is disposable and
has instantaneous detection and classification of pathogens. The three pathogens this
biosensor can detect are Salmonella typhimurium, and the Escherichia coli strains
JM109 and DH5-α. There are three main components that play various roles in
detecting pathogens, as seen in Fig. 4. The sensor itself consists of silver electrodes
which are assembled onto plastic polyethylene terephthalate (PET) substrate by a
Fujifilm inkjet Dimatix material printer (Fig. 5). Silver nanowires are then added onto the
electrodes increasing the sensitivity of the sensor. Connected to the sensor is an
impedance analyzer which measures changes to the impedance of the sensor(Ali,
2018). After the reading, the impedance analyzer sends the recorded data to the
computer which is displayed. To operate the system, a small sample of water taken
from the aquaponics system is placed on the sensor. Based on the concentration of
pathogens present, the impedance levels will be recorded and displayed accordingly.
This system is cost effective and simple to use. If a pathogen is detected, the proper
protocol to treat the pathogen should be utilized.
Implementation of System in Namibia:
Figure 7. Map of Namibia (ExpertAfrica)
Figure 8 (a): The photo shows one of the two reservoirs located on the rural farm that the aquaponics
system will be constructed next to (Cline, 2018).
Figure 8 (b): This picture depicts the environment and basic set-up of the farm in Namibia (Cline, 2018).
The aquaponics system was designed with the Namibian climate and environment in
mind. To ensure the system will succeed in the desert-like area, the tilapia are native to the
country, and the selected plants will be accustomed to hot weather and arid climate. The
structure of the box is sturdy to withstand the weather in the area. With little vegetation to feed
the livestock, the aquaponics system will assist providing nutrition to farm animals.
Advantages and Disadvantages:
This aquaponics system design is a simplistic structure that would not be complicated to
replicate should the farmer want to expand. Also, the necessary materials are cheap and
affordable. This design meets the client’s preference to start on a smaller scale to experiment
with the effectiveness of an aquaponic system in the area. One problem with the design is the
plant and fish production has a small potential due to the small-scale structure of the design.
The fish are also going to be in a tight proximity. Water flow is controlled to an extent, but there
could still be enough stagnant water in the fish tank that the ammonia and nitrate levels could
affect the fish.
Design Recommendations:
The RCAT team recommends this small, simple design to observe how successfully the
system can be integrated. The system can independently function on its own, with the exception
of a source of food for the fish, which will need to be provided by an outside source. The fish
and plant components are kept in close proximity to ease the flow of the system and make it
simpler to construct. Additionally, the symbiotic relationship between the plants and fish are
easier to maintain and observe.
Testing Needs:
To ensure the selected aquaponics system would be successful in Namibia, there are preliminary
tests to judge the overall performance of the design. The system will be put in an environment similar to
the desert-like region to test the functionality and temperature regulation. This will also test the durability
of the system to withstand harsh weather conditions. To ensure the compatibility between the fish and
plants, one full production cycle of both the fish and plants will be observed. The data collected
throughout this test will provide a real-world timeline of how the system will perform in Namibia. During
the test, the fish will be observed on how they deal with stress. An individual who is inexperienced in
operating aquaponics systems will be selected to operate the proposed system. This individual will
provide feedback on how to further simplify system components.
Summary:
In conclusion, RCAT was able to design a simple plant-over-water aquaponic system that
consists of a fish tank, growing bed, filtration system and detached biosensor. When designing
the system, the team took into account all of the client’s needs and constraints regarding the
climate, geography, and regulations of Namibia. The system was designed specifically for the
Namibian climate and culture, utilizing Tilapia and cowpeas, both of which are produce that can
be found locally in Namibia. In the end, the team was able to design a system that met the clients
most important constraints by serving as a cost-effective, low-maintenance aquaponics system
that would supply enough food for a herd of sheep on a farm in Namibia. Should the farmer want
to expand in the future, the design would be easy to replicate. Overall, the design successfully
accomplished all the criteria and should aid the farmer in Namibia.
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