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Commercial Trial Integrated Aquaculture “Aquaponics”

Mr Tony Bart, an Aquaculture Lecturer with Challenger Institute of Technology, together with Bruce Ginbey, the Production Manager at the Australian Centre for Applied Aquaculture Research and Peter Graham, a horticultural Lecturer have built and operated a successful commercial trial “aquaponic” system since April 2011 at the Institutes Murdoch campus, Western Australia. Sidenote: We are pleased to announce, this article was published in the latest edition of Austasia Aquaculture Volume 25 No.3 Spring 2011 page 42 in collaboration with John Mosig.  There are a few “extras” in this version you will enjoy. The system integrates two 5000 liter tanks for aquaculture with filtration and a 1600 hole nutrient film technique (NFT) hydroponic system which consistently produces 400 head of lettuce every four weeks from seedling. Introduction I met with Tony at the Murdoch campus to view and discuss the workings of this system which is still undergoing transformation as more knowledge is gathered about the nutrient requirements of the plants and the filtration capacities of the system.   Tony gracefully permitted, and encouraged us to publish the details about this highly productive system to encourage the wider commercial aquaculture community to take a closer look into options available for alternate source of income and reduction of nitrogen and phosphorous effluent discharge. The potential of these types of systems are still widely unknown, however there is a number of large to commercial systems being built-in Australia 2011 and 2012 which will give us a greater understanding of their capacity to earn or at the very least offset rising fish feed costs. The Aquaculture principles applied to the Murdoch System pioneered by Challenger will help shape the future of this type of Integrated Aquaculture in Australia with the support and collaboration of the leading educational institutes around the country including the Freemantle Campus and industry support bodies. Materials The system has been put together with low capital cost in mine and all the filtration systems and functions have been custom-built by the Institute.  The diagram below lays out the primary components and how the water flow is now configured. Each side is made with the following components available at the time of construction with some common components.  Not all the materials such as pipes and valves have been listed.  These are the major materials. Single Components x 2 Shared Components x 1 Aquaculture tanks 5000 liters x 1 Custom Polygeyser type bead filter x 1 Custom Swirl separator  x 1 Ebarra Best Zero Submersible Pumps with float switch x 1 NFT 6meters with 25 holes each x 32 Sump tank 1000 liters x 1 Esam Uni Jet SPCE 40 side channel Blower Diaphragm Pump 150L/m Hotco 2kw Immersion Heater Battery Backup System 2 Hours Methods Water circulation: The water is circulated throughout the system via the two submersible pumps in the sump.  These pump water from the sump to both the aquaculture tanks and the far end of the nutrient film hydroponic channels. The water to the hydroponics is pumped through a buried 40mm pressure pvc pipe to each set of 8 lengths of NFT with a valve to control the flow on each set of channel.  The PVC is converted to 25mm black irrigation poly pipe and each channel is supplied with a 4mm poly tube.  The water runs by gravity through the bottom of the channels to a 50mm PVC manifold which discharges into the aquaculture tank. The aquaculture tank is supplied water directly from the submersible pump in the sump via a 40mm PVC pipe with a valve for flow control into the culture tank. Effluent water exits the culture tanks via three outlets.  The two primary outlets have a plastic screen covering the 50mm PVC outlets and both skim water from the surface of the culture tank and both enter the custom polygeyser type bio filter via uniseals. The secondary, smaller outlet is the primary solid waste outlet made up of 40mm PVC which extends up from the bottom, center of the aquaculture tank at 45 degrees and exits the aquaculture tank at the top and gravity feeds into the swirl filter.  From the swirl filter the water exits via a 50mm pipe and enters the custom polygeyser type bio filter through a uniseal. The water from the bio filter exits by gravity via uniseals and 50mm pipe through two outlets and is converted to 90mm pipe at a tee and both gravity feed to the in ground sump. Filtration: The primary solids filtration is provided by a custom swirl filter made up of 300 mm diameter PVC.  The 40 mm outlet from the culture tank enters the side of the 300mm pipe at the tangent about half way down the length of the filter.  This creates the vortex to spin the heavier solids out of suspension.  The water is then skimmed from the top of the filter via a screened 50mm outlet to the custom polygeyser bio filter. The swirl filters have a conical bottom which collects the settled solids and this waste is dumped to the solid waste sump outside the hot-house once a day using a valve at the bottom of the filter. Bio filtration is achieved with the use of a custom polygeyser type bio filter utilizing 50kg of polyethylene chips.  The bio filter is backwash with air four times a day using 300mm diameter cylinders in the bottom of the sump pressurized by the small diaphragm pump until the desired pressure is reached and a relief valve releases the air into the bio filter to agitate the plastic bio media to dislodge any buildup of solids.  The waste water gravity feeds to the solid waste sump outside the hot-house. Heating: Due to fish species selection and winter site temperatures the culture tanks require heating to above 20c.  Primary heating is achieved with the thermal capacity of the hot-house.  Secondary heating is with a small solar/battery operated submersible pond type pump in the main sump.  The water from the sump is pump up to 80 meters of 13mm black poly irrigation pipe circled on the insulated lid of the culture tank and then into the culture tank.  The solar system is set to run only during daylight hours. To facilitate insulation against heat loss the culture tanks have a 50mm open cell polystyrene lid and water is not pumped through the hydroponic system at night. A 2 kilowatt submersion heater provides backup heating  in the sump which is thermostatically controlled to support temperature in the colder months. Hydroponic Subsystem: Using 32 x 6 meter lengths of NFT channel, consisting of 25 holes each spaced at roughly 240mm.  These are a standard hydroponic channel.  Nutrient rich water is pumped from the main sump to a manifold on each set of 8 channels and gravity fed through the bottom of the channels and exits directly into the fish culture tanks stripped of nitrogen and other nutrients by the plants. Results Plant Production: The plants are being propagated by the horticulture department glass houses at the campus in rock wool cubes, which takes 2 weeks to be ready to transplant to the hydroponic system.  Several varieties of lettuce are being trialed with success.  The system of planting is staggered in four-week intervals to allow harvest of 400 lettuce every week for a total production of 1600 lettuce a month.  Each week 400 lettuce are harvested and sold and new two week old seedlings are planted out in their place.  This staggered planting allows for a constant nutrient level in the system and removes the risk of nitrogen spikes. Fish production: As barramundi are outside their natural range, the system must support a temperature that is more suited to their best growth.  In this case the water temps are kept above 20C to prevent stress to the animals through the use of various heating as described earlier.  The barramundi have not yet been grown to market size yet as the system has only been running since April and has gone through five months of cooler climate conditions reducing the feed uptake and growth of the fish. However,  one 5000 liter tank has 280 x 200gram fish (56kg) and the other 5000 liter tank has 80 x 500gram fish (40kg) for a current total of 96kg of barramundi grown from fingerlings supplied by the Marine Institute Barramundi Hatchery facilities at Freemantle. Feeding: On average, depending on water temperatures, each tank is fed 300grams of Skretting “Nova ME” sinking pellets, (45% protein, 20% lipid) which is 0.75% to 0.5% body weight per day.  The low feed rate is reflective of the water temperatures of 22C at this time of year.  This provides about 16grams of Total Ammonia Nitrogen per day for the volume of water in the system, which is about 11m3.  This nitrogen dilution is in line with University of Virgin Islands aquaponics trial results. Water Quality: Water quality test results carried out on the water in the main sump on the 4th of August 2011 by a spectrophotometer and titration kits are as follows: pH 7.24 Temperature  22.6 Co Alkalinity  67.122mg/L Ammonia by test kit  0.0mg/L NH4+ Nitrate by test kit  65mg/L NO3- Nitrite by test kit  0.70 mg/L NO2- DO2 80% Saturation The addition of Calcium hydroxide is used regularly to support pH and alkalinity levels between 6.8 and 7.2 and to a lesser extent potassium hydroxide, because no fruiting plants are grown. Labor and Time: The day to day tasks consist of feeding the fish, flushing the filters, harvesting plants and planting seeds and seedlings.  In general on days where no harvesting or planting occurs 15 minutes in needed to feed and observe the fish and flush the filters.  On one day a week planting, harvesting and packing is required.  Most weeks the time spent is one person 4 to 5 hours a week. Discussion: There is further scope to increase the production of this system as the fish tanks are not yet running to capacity.  The 9.6kg/m3 is a relatively low bio mass for the tank volume (0.96%), however as the smaller 280 x 200gram fish come into market size at 500grams, the system will be operating at 18kg/m3 density, still below commercial capacity.  The increase in standing stock bio mass will increase the capacity for the hydroponic system to be expanded. If the standing stock bio mass was increased to 180kg and the water temps were maintained at 27Co an increase of feed rate to 1%bw/day (1.8kg per day), the TAN production is estimated to 53grams per day, which is 3 to 4 times higher concentration than is required by the hydroponic subsystem for strong plant growth. The hydroponic subsystem could be tripled to 4800 holes as the standing stock is increased to 180kg and temperatures remain consistent to harvest 1200 plants per week which will bring the system into commercially relevant capacities. An expansion of the hydroponic subsystem is being considered in the future of an extra 800 holes as the current plant capacity still has excess nitrate (65mg/L). Automation of the draining on the swirl filters can be managed with automatic valves and auto feeders for the daily task of feeding the fish. Considering the low-budget and ingenuity with which this highly productive system has been build, it provides an excellent example of the relative simplicity and low capital investment required to achieve commercially relevant results. Regards Paul…

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