Monthly Archives: October 2011

CCRES AQUAPONICS Systems


AquaPonics Systems

by our Aquaponics friend

Frank De Block-Burij

from
AquaPonics in Europe

 

 

 

 

Nutrient Film Technique (NFT)
Barrrel Growbeds
Rectangular Growbeds
Floating Rafts (DWC)

There are as many AquaPonics setups as there are Aquaponics enthousiasts.

Most of these are based on three main AquaPonics systems:

Nutrient Film Technique (NFT).

Growbeds filled with media.

Floating Rafts or Deep Water Culture (DWC).

Each system has it’s advantages and drawbacks.
Of course these systems can be combined in a setup.
This will often lead to a win-win situation.

Nutrient Film Technique (NFT).

Nutrient Film Technique or NFT is a well known technique in hydroponics.

A shallow stream of water is recirculated in a channel past the bare roots of the plants. This water contains all the dissolved nutrients that plants need for their growth.

Plants are grown in small pots filled with media that are inserted in holes in the gutters.

Growbeds filled with media.

Growbeds are the most repanded AquaPonics system: water from the fish tank is pumped to containers in which the plants are grown on media.

These media serve a quintuple purpose:
– to serve as support for the plants.
– to ensure nutrients to be accessible to plant roots.
– to ensure oxygen to be accessible to plant roots.
– to aerate the water flowing back to the fish tank.
– to ensure biofiltration and nitrification to make the water reuseable for the fish.

To achieve all this, flood and drain is the preferred method.

Floating Rafts or Deep Water Culture (DWC).

DWC uses tanks or ponds to grow plants in on floating rafts.

Plants are grown in small pots filled with media that are inserted in holes in the rafts that keep them floating on the water surface, only dipping the roots in the nutrient rich water.

The main advantage of this system is the ease of planning, sowing and harvesting of one particular fast growing crop, i.e. lettuce and herbs: very long “raceway” ponds are calculated so that the harvesting of one or more rafts coincides with the sowing of new ones.
These raceways can be as long as 100 and 200 m.

More info at: solarserdar@gmail.com

CCRES AQUAPONICS
CROATIAN CENTER of RENEWABLE ENERGY SOURCES (CCRES)

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Aquaponics VS Hydroponics by CCRES AQUAPONICS

Why Is an Aquaponic System Better than a Hydroponic One

Hydroponic gardens are already highly popular among people of all ages. They require little space, are easy to take care of and give satisfactory results. However, because you will need to supply the water with necessary nutrients, which are most of the times chemical, the taste of the crops is not quite the ones people expect. Also, people trying to switch to organic products have a hard time in coping with the chemical additions from the hydroponically-grown vegetables. Fortunately, a new type of gardening is available. It is called the aquaponic system and can help you grow organic food in your home.

The aquaponic system is a mixture between the aquaculture, as it requires growing fish in a special fish tank and hydroponics, as it involves growing plants with water and nutrients. You will probably wonder what role the fish play in all this business. Well, things are quite easy: the fish excrements contain ammonia which is later decomposed in nitrites and nitrates. The latter substance is benefic for the plants, offering them enough nutrients to grow and develop normally. Thus, there will be no need to supply your plants with chemical substances as they will already have all the food they need.

This leads to the several advantages that the aquaponic system has over the hydroponic one. First, the vegetables will have a better taste as they will grow only with natural food and at their own peace. This will give them that delicious taste you love so much in veggies. Then, the system is simpler, as you will no longer need to feed your plants each and every day. Just make sure that your fish are in good shape and then let nature take its course.

Last, but not least, with the aquaponic system you do not only grow vegetables, but you also have fish which you can use for decorative purposes or you can very well cook delicious meals for you and your family.

Aquaponics is an improved version of the hydroponic system. The crops are better and the process is easier. In addition to that you get to eat organic food!
More info at: solarserdar@gmail.com

CCRES AQUAPONICS

CROATIAN CENTER of RENEWABLE ENERGY SOURCES (CCRES)

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Types of biofilter by CCRES AQUAPONICS

Sizing a Biofilter

Sizing a biofilter can be a daunting task for the novice in the aquaculture industry.One has to pick and choose between many technologies and options.Once you have chosen a type of biofilter there are still a tremendous number of variables to consider and make decisions about.Due to the wide disparity in the data reported in the literature, it is wise to oversize biofilters or provide for a modular design that will allow for expansion. Trickling filters are relatively easy to design and build.Here is an example of a simplified procedure for a trickling filter that may help to start the design process.

1.Estimate the maximum amount of feed you will be feeding your fish at any time in the crop cycle.This will determine the maximum load the biofilter will need to handle.

2.Decide or determine the TAN (total ammonia nitrogen) level that your fish will be able to tolerate with no ill effects.Based on the allowable ammonia concentration in the culture tank, determine the ammonia removal rate.Make a guess about the hydraulic loading rate that you will use.See Graph 1.

3.Decide on the amount of water that will flow through the biofilter..One way to look at water flow is to calculate how long it will take for all of the water in the culture tank will pass through the filtration system.A very slow system might recirculate all of the water in 12 hours.A very fast system might recirculate all the water in 5 min.A good starting point for a lightly loaded system might be a 1 hr. turnover time.In other words, all the water in the tank is passed through the filter in 1 hour.For example, a 5000 gallon tank would need a flow rate of 5000 gallons per hour or 83 GPM.

If you are adding oxygen with a system that is external to your culture tank, your recirculating flow rate will probably be determined by the oxygen requirements of the fish.If your oxygen addition is within your culture tank, then the solids removal and biofiltration will guide your flow rate.

4.Based on the amount of feed to be used and the ammonia removal rate, calculate the total amount of surface area required for the biofilter packing.

5.Decide on the density or SSA (specific surface area) of the biofilter material.The three commonly used SSA’s for structured media are 119, 69 and 48 ft2/ft3(390, 226 and 157 m2/m3).

6.Divide the total amount of surface area required by the SSA of the filter material.This gives you the volume of biofilter media required.

7.Decide on the shape of the biofilter.

8.Determine the hydraulic loading rate.If the hydraulic loading rate is too low, either increase the water flow or make the trickling filter taller and narrower.The hydraulic loading rate influences the ammonia removal rate as shown in graph 1.In addition, there is a recommended minimum water loading rate based on the specific surface area of the media.The more surface area in a given volume, the more water is required to fully wet all the surfaces.

Specific Surface areaMinimum Water loading

Sq.ft./cu.ft.GPM/sq.ft.

303

504

705

1207

The sq.ft. in the water loading refers to the plan area (top area) of the trickling filter.The sq.ft. in the specific surface area refers to the surface contained in the packing or media.

Graph 1

This graph is based on the data presented in the very useful paper by Kamstra, Van der Heul and Nijhof “Performance and optimization of trickling filters on eel farms”Aquacultural Engineering 1998 p. 175 – 192.This graph gives approximate removal rates for warm, freshwater trickling filters with good water distribution and sufficient dissolved oxygen.Saltwater systems will have lower removal rates and cold water systems will have lower removal rates.New systems will have lower removal rates.Systems that have wide swings in ammonia concentration will have lower removal rates.Nitrifying bacteria are inhibited by light so filters exposed to bright lights will have lower results.Systems using various therapeutic agents like formaldehyde can have lower results.Use this graph with caution !!You may get better results but you can also get worse results.It is much better to include a generous safety factor than have a system limited by the biofilter.Lower ammonia concentrations are always better than higher concentrations. To the best of my knowledge, no fish ever died as a result of an oversized biofilter but many have died from undersized ones.

Here is an example of a sizing calculation:

Crop Size500 kg (1,100 lbs.) of fish

Feeding rate2% bw /day

Amount of Feed 10 kg(22 lbs.) at 32% protein

Allowable TAN1.5 ppm

Water Flow83 gpm

Amount of Ammonia Produced.03 x 10 kg = 300 gm/day

Ammonia Removal Rate.6 gm/m2-day at 6 gpm/ft2 hydraulic loading rate

Surface area required(300 gm /day)/( .6 gm/m2-day) = 500 m2

Convert square meters to ft2500 m2 x 10.76 ft2/m2 = 5380 ft2

Packing density or SSA69 ft2/ft3 (226m2/m3)

Volume of media=(500 m2)/(226 m2/m3)=2.21 m3

or

Volume of media=(4035 ft2)/(69 ft2/ft3)=78 ft3

If we start with a stack of media 4 ft wide by 4 ft long by 5 ft high we get 80 ft3.Using the 83 gpm flow rate, the hydraulic loading would be about 5.2 gpm/ft2

Hydraulic loading83 gpm/(4′ x 4′) = 5.2 gpm/ft2

This is higher than the minimum hydraulic loading rate for this media but lower than the 6 GPM/ft2 we guessed at when reading graph 1.The easy thing to do is to increase the water flow rate slightly to 96 gpm(4′ x 4′ x 6 gpm/ft2).

The above procedure is a simplified, general guideline for the process of designing a trickling filter.Predicting the amount of packing required for a given application is not an exact science. If the filter is undersized for the application, the level of TAN at design conditions may be higher than desired.Generally, it is wiser to oversize a biofilter rather than undersize it.Fish will not die from an oversized biofilter.

Other Design Concerns

One of the most important considerations in any biofilter design is providingall of the bugs (micro organisms) with a constant supply of food (nutrients) and oxygen.The reason the word “all” is emphasized because many biofilter designs do not distribute the flow of food and oxygen evenly.Some parts of the biofilter may have a high flow of water past them and other parts may have almost no flow.This is a common cause of poor performance by a biofilter.

Even hydraulic loading (water flow) throughout the filter is extremely critical to proper utilization of the biofilter media.Rotating Biological Contactors (RBCs) are consistently shown to have very high treatment efficiencies.This is because the media is consistently and evenly moved through the water to be treated.All of the bugs on the surface area contained in the RBC are exposed to a steady stream of food and oxygen.Trickling filters and submerged filters can achieve high treatment efficiencies if they also have a constant, even flow of water to all of the surface area contained in the filter.

Trickling Filters

We will begin the discussion of design with trickling filters because they are easier to design and size than a submerged filter.Once the size and shape of the trickling filter has been decided, the water distribution system must be designed.It cannot be overemphasized that the water must be evenly distributed over the top of the media.Areas that are dry will not provide any biofiltration benefit.In addition, the interface area between the wet and dry areas will tend to accumulate solids and eventually lead to plugging.In general, it is easier to evenly distribute the water for systems with high hydraulic loadings compared to low hydraulic loadings.There is no maximum water loading for structured packing.

There are two common ways to get an even distribution using a fixed spray system.For square or rectangular vessels one way is to use solid cone, square pattern spray nozzles.The edge of each spray pattern should touch the edge of each adjacent pattern.This system is easy to visualize and design.The only requirement is that the nozzle spray pattern must be well defined by the manufacturer so that the designer can size the system properly.The most common drawback to this system is that not all nozzles have an even spray pattern even though they are sold as solid cone nozzles.Very often the center of the spray pattern has a lower water loading than the edge of the pattern.

The second way to get an even water distribution is to use many over lapping spray patterns.Often, the individual nozzle spray pattern is hollow but the combination of many patterns covering the same spot gives an even coverage.The main problem with this system is that the wall of the vessel will intercept a certain amount of water. Any water that hits the wall will generally not go through the filter media.In a very large vessel, this is not a problem because the ratio of the perimeter to the area is small.In small vessels this system will not work well.

There is a third method of distributing water that can be used in round vessels.Rotating arm distribution systems can give an even distribution if they are sized properly.Theyalso have a low head compared to some spray systems.The drawback to rotating arm systems is the wear and tear on moving parts and the required maintenance.

Part of the art of designing a trickling filter is to balance the competing requirements on the design.

1.In order to keep the energy costs to a minimum, the pumping head for the filter should be as low as possible.The maximum plan area covered by the filter is determined by the minimum water loading.

2.In order to minimize the floor space used by the filter, the filter should be as tall as possible.The practical limitations are the height of the building, the head limits on the pump and the structural and stability considerations of the vessel.

3.A taller filter will have a longer flow path for the water.This means a more complete treatment of the water with each pass.

4.Taller filters will have higher specific water loadings.This means better flushing action, more turbulent water films and higher ammonium removal rates.

Trickling filters for industrial applications are sometimes 30 ft. tall.This is not practical for aquaculture systems.In general, trickling filters for aquaculture are between 3 and 10 ft. tall.

Submerged Filters

Submerged filters are excellent choices for small systems because they are very versatile.They can be located in a separate tank or in the culture tank. They can be horizontal flow, up flow or down flow.They can be aerated or not.The most important consideration for the designis the even distribution of water to the packing.It is very common for submerged filters to be designed as large, flat and thin sections of packing with water direction being up flow or down flow.There is typically no provision for distributing the water to all areas of the media.The length of the water path through the media is very short and the resistance to flow is very low.This is a recipe for disaster.The water flow will short circuit though a small section of the media and the rest of the biofilter will become anaerobic.

Ideally the flow path through a submerged filter should be as long as possible.A long thin raceway is the best.This type of biofilter is known as a long path, plug flow submerged filter.(see the paper written on this filter type). Another possible alternative is the use of aeration to induce a circulating flow around a tank.The key to properly designed submerged biofilters is the velocity through the media.The goal should always be to provide a high enough velocity through the media so that the flow is turbulent and all of the media has an equal flow of water.Equal flows of water insure a fresh supply of oxygen and nutrients to all of the bugs on the surface of the media.

More info at: solarserdar@gmail.com

CCRES AQUAPONICS

CROATIAN CENTER of RENEWABLE ENERGY SOURCES (CCRES)

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Trickling filters and CO2 strippers by CCRES AQUAPONICS

CCRES AQUAPONICS

Getting Full Performance from Trickling Filters and CO2 Strippers with the Right WaterDistribution System

Trickling filters and CO2 strippers are common devices in recirculating aquaculture systems.They are often referred to as packed towers.The performance of these towers is controlled by:

  • The type of packing or media
  • The amount of packing
  • The shape of the vessel
  • The ratio of air to water
  • The temperature
  • The distribution of air through the tower
  • The distribution of water through the tower

The distribution of water is the most commonly neglected and least understood aspect of the design of packed towers.Poor water distribution is often the primary cause for poor performance and high maintenance costs for packed towers.A well designed tower will have an even water distribution across the entire packing surface.For a biofiltration system, this gives all of the microorganisms an equal and consistent supply of nutrients and oxygen.For a stripping tower, even water distribution provides a uniform water film on all of the packing for maximum gas transfer.

Poor water distribution can lead to the following problems:

  • Loss of performance due to dry surfaces in the packing bed.
  • Loss of performance due to air bypass through the dry areas.
  • Erosion of the packing due to locally heavy hydraulic loadings.
  • Plugging of the packing due to scale deposits in the intermittently wetted areas

If the water distribution is not done correctly, no other changes will bring the tower up to full performance.On the other hand, improving the water distribution in a tower is a very cost effective way to get more performance out of a system.Although the water distribution system is a key element in the design of a tower, it is a relatively small part of the system cost. Usually, it is less than 10% of the cost.If a distribution system only wets half of the media, the tower must be twice as large to get the same performance as a system that gives complete coverage.It cannot be overemphasized that an even distribution of water is essential to obtain full performance from a packed tower.

Water distribution designs that are less than optimum include the use of the following methods:

  • A single pipe that dumps water in the center of the vessel.
  • A pipe with a few large holes drilled into the bottom or side.
  • A pipe with multiple small holes drilled into the bottom or side.
  • A grid or drip plate.
  • A system of troughs or launders with notches cut into the edge.
  • A single, hollow cone nozzle.

Here is a worse case example.Water is dumped from a pipe at a single point into a vessel.

Spreading the water out evenly doesn’t happen by accident or magic.A good water distribution system will typically consist of one of the following three designs:

Design 1. – A piping system with square pattern, solid cone spray nozzles.The spray patterns touch at the edges.

Design 2. – A piping system with round or square hollow cone spray nozzles.The nozzles will be spaced to provide overlapping patterns.

Design 3. – A flat pan or tray holding a few inches of water with target nozzles installed in the bottom.The spray patterns from adjacent nozzles will overlap.

There are advantages and disadvantages for each type of system.

Design 1

This system is simple to design and relatively easy to construct.It can provide even coverage depending on the quality of the spray pattern.The use of a pipe system allows for unrestricted air movement and relatively easy access to the packing media.The main disadvantage is that these systems typically require higher head pressures to operate well.The pressure drop through the nozzles is usually around 5 – 15 ft. of H20.

Design 2

This system is also simple to design and relatively easy to construct.If it is done properly, it will provide a very even water distribution.Head loss will be equal to or less than design 1.The disadvantage of this system is that a larger fraction of the water will impinge on the wall of the vessel.If the vessel is large then this wall fraction will be relatively small.If the vessel is small however, this fraction can be more substantial.

Design 3

This system can be a little more complicated to design due to the structural requirements.The weight of the water in the pan must be well supported.The big advantage to this design is the very low head requirement.Pan type systems can operate with 12″ of total head loss.Other disadvantages of this system are the restriction of air flow for counter flow towers and the difficulty of observing or accessing the media.

Nozzle requirements

The ideal nozzle for our applications will have:

1.An even water distribution pattern

2.An open, clog resistant flow path

3.A low head loss

4.A low cost

5Standard pipe thread attachment

6.Good impact resistance

7Corrosion resistance to salt water

8.Good performance under a wide range of flow rates

A nozzle should not:

1.Provide a fine mist or fog of small droplets

2.Have small, easily clogged flow passages.

3.Throw the water a long distance.

4.Have moving parts.

This is an example of a nozzle that fits the Design #1 system.This picture shows the bottom of the nozzle.The cost of this nozzle is about $15.00.It has a 2″ male NPT connection. It is injection molded from ABS or polypropylene.

Here is a round pattern nozzle for Design #2.The cost of this nozzle is about $4.00.It has a 1.5″ male NPT connection.It is injection molded from polypropylene.

This is a square pattern nozzle for Design #2.The cost of this nozzle is about $4.00.It has a 1.5″ male NPT connection or a 1.5″ self taping, tapered thread.It is injection molded from polypropylene.

Here is a nozzle for Design #3.This nozzle fits in a hole in a pan.It has a two piece design that locks itself into the pan.Typical spacing is 4 – 12 inches on center, depending on water loading.The cost of this nozzle is about $4.00.It is injection molded from polypropylene.

In order to design a good system, one needs good data.Here is a typical flow vs. pressure chart.This chart allows the designer to choose the number of nozzles that are needed for a given flow at the available pressure.If the flow per nozzle is known, one can determine the head loss through the nozzle.Although the pressure is shown on the X axis, it is the dependent variable.

After the number of nozzles, operating pressure and flow is known, the correct spacing above the media must be determined.A diagram showing water spread is very helpful.Here is a typical example.

Design Example 1

Using the above charts we can design a distribution system for a typical CO2 stripper.The proposed tower has a 4 ft. x 4 ft. plan area and a flow rate of 232 gpm.If we divide the tower into 4 equal squares of 2 ft. x 2 ft. then the flow per nozzle will be 58 gpm.Using the chart for flow vs. pressure we see that a nozzle with an orifice of 1.375 in. will have a pressure loss of 4 ft. H2O.Since the pattern is 2’ x 2’, the distance from the center of nozzle to the edge of pattern is 12”.Using the spread chart for the 1.375” orifice we see that the bottom of the nozzle must be about 9 from the media to get the 12” horizontal spread.

Design Example 2

For this example let us design a pan distribution system.The tower is 4 ft. x 6 ft. plan area.The water flow rate is 200 gpm.If we space the nozzles 8” on center and 8” from the walls there will be 5 rows of 8 nozzles for a total of 40 nozzles.The flow per nozzle will be 5 gpm.Using the chart below there is a choice between two nozzles.The .75 in orifice will require a head of 6 in. of water in the pan.The .875 in orifice will require 3.5 in. of H2O in the pan.The usual vertical spacing for these types of target nozzles is 2- 4 inches from the bottom of the nozzle to the media surface.

Summary

Good water distribution is a critical component of packed towers design.Fortunately, it is relatively easy and inexpensive to do it right.In most cases, it is also possible to retrofit a good system into an existing tower.Consult with your tower or media supplier to improve the performance of your trickling filters and CO2 strippers.

More info at:solarserdar@gmail.com

CCRES AQUAPONICS

CROATIAN CENTER of RENEWABLE ENERGY SOURCES (CCRES)

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