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Beit Qad Commercial Aquaponic system
Technical Manual
Philip Jones April 2013
Beit Qad Commerical Aquaponic System
Technical Manual
By Philip Jones
© Byspokes and Ma’an Development Centre, 2013 All text, illustrations and photos by Philip Jones. www.byspokes.org [email protected]
Table of contents
SYSTEM OVERVIEW 1
SYSTEM COMPONENTS 2
Fish tanks 2
Solids filtration 3
Biological filtration 4
Mineralisation 6
Hydroponic component 7
Seedling production 8
Pumping and aeration 8
MANAGEMENT 10
Cycling 10
Aquaculture system 10
Hydroponic system 11
Water quality 12
SYSTEM OPERATION 13
Daily tasks 13
Weekly tasks 13
Monthly tasks 13
TROUBLESHOOTING 14
DIRECTORY 15
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System overview The commercial aquaponic system designed for the Beit Qad demonstration site consist of two interlinked components; a recirculating aquaculture system (RAS) and a hydroponic system. The two systems are linked by a double sump tank which has been designed to allow for the RAS and hydroponic components to be operated independently (as aquaculture and hydroponic systems) or together (as an aquaponic system). The RAS component has been designed to be a “low head” system – i.e. with minimal vertical height difference between the maximum and minimum water levels across the components. This is to reduce the energy required for pumping water.
Figure 1: Overview of the aquaponic system showing aquaculture component (left) and hydroponic component (right). When both components are operating together, then dissolved nutrients from the aquaculture wastes are delivered to the hydroponic component to be taken up by plants. During independent operation, nutrients from the aquaculture system are not passed to the hydroponic system and so supplementary hydroponic nutrients must be used. However, enabling the two systems to be operated independently greatly enhances the system’s resilience; a problem in one of the systems may be isolated without risking the other system.
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System components
Fish tanks The aquaponic system consists of four separate round fish tanks each of approximately 2.1m3, thus the total fish tank water volume is around 8.4m3. The fish tanks are constructed from standard, 2.5m3 (1.46m diameter) water storage tanks (white, to reduce heat gain in the summer), which have been opened by cutting off the top, just below the shoulder (1cm above the uppermost moulding line). The fish tanks are positioned close to each other in order to be able to share common drain and influent pipe main lines. The fish tanks are all levelled with each other, and excavated slightly into the ground (floor height -‐40cm) in order to facilitate levelling of the other, shorter, components.
Effluent water is drawn from the bottom centre of the fish tank using a “solids lift overflow” which sets the maximum water depth in the fish tank to 135cm. The overflow pipes (50mm diameter) from all the fish tanks extend outside the tanks towards a central point between the tanks where they are united by a 110mm collector trap. The common drainage is by 110mm pipe from this point. Influent water is delivered to each fish tank at a height just above the water surface level, at a rate of around 3m3/h (to fully exchange fish tank water volume 1.4 times per hour). The water is delivered parallel to the fish tank wall in such a way as to set up a clockwise rotational current within the tank. This circular flow facilitates settling of the solid wastes in the bottom centre of the fish tanks.
Figure 2: Fish tanks being put into place (left) and detail of common fish-‐tank drain (right).
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Solids filtration Coarse solids are removed from the system via a “radial flow separator”. The radial flow separator works by forcing the water flow to change direction and velocity, which encourages solid particles to settle out. Radial flow separators are very space efficient when compared to standard, gravity based settling ponds, and typically operate with loading rates of 10m3/m2/hour. Thus, to match the fish tank effluent flow rate of this system (12m3/hour), a radial flow separator of 1.2m2 surface area is needed. The radial flow separator is also constructed from a white, standard water storage tank (1.5m3; 1.35m diameter -‐ thus 1.4m2 water surface area) with the top removed. The top of the water tank is inserted upside-‐down into the tank to make a slightly conical, funnel like false floor to facilitate collection of all solid wastes in the centre. The tank is positioned such that the upper rim level, and water surface level are the same as those of the fish tanks.
Figure 3: Design of the radial flow filter, showing major components and internal layout.
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The fish tank effluent water enters the radial flow separator via a 110mm pipe which extends into the centre of the separator, where there is an upward facing elbow, directing water flow vertically upwards. Around this elbow is a radial flow column made from a 200L blue barrel, which extends slightly above the water surface level. This forces the incoming water to change direction from up-‐flowing to down-‐flowing. Once the water flows beyond the lower end of this radial flow column, it changes direction once again and flows upwards. With each change of direction, the velocity of the water also decreases, which gives solid wastes the chance to settle to the bottom of the separator by gravity. Water exits the radial flow separator via a 110mm pipe positioned just below the water surface level. Solids can be periodically drawn out from the bottom of the separator via a sludge drain, made from 50mm pipe drawing from just above the bottom centre of the separator. Sludge is discharged to a mineralisation tank where it can be converted back to liquid plant nutrients. In addition to this coarse solids separator, all water passes through a 60μm in-‐line filter before reaching the hydroponic component. Biological filtration Biological filtration (the conversion of toxic ammonia in fish wastes into nitrite and then nitrate) is achieved by a “Moving Bed Biofilm Reactor” MBBR. MBBRs are relative newcomers to the aquaculture industry. MBBR technology uses thousands of polyethylene biofilm carriers (Error! Reference source not found.) operating in mixed motion within an aerated wastewater treatment basin. Biocarriers provide a very large, protected surface, which supports the growth of heterotrophic and autotrophic bacterial communities. The specific surface area (SSA) of biocarrier media is typically around 500m2/m3.
Figure 4: Constructed radial flow filter
Figure 5: Kaldness type biomedia
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However, MBBRs function best at fill rates below 70% (usually 40-‐60%) as this ensures adequate movement of filter media within the MBBR. Effective surface area within the MBBR vessel is therefore 200-‐300m2/m3. TAN (total ammonia nitrogen) removal rates fluctuate depending on a range of environmental factors (pH, alkalinity, temperature, DO, BOD of influent water) but for the purposes of this project can be assumed to be in the region of 1g/m2/day. Another advantage of the MBBR is that it allows for supplemental oxygenation and CO2 stripping of the wastewater – further enhancing the quality of effluent. Daily TAN production is directly related to the amount of food given, and the protein content of the food, and can be calculated using the following equation: TAN = Feed weight x Protein content x 0.092 Time It is proposed to use 32% protein feed, delivered at 2% body mass (for a standing crop of around 200kg) in this system. The daily total feed is therefore around 4kg. This gives a daily TAN production of 118g. 118m2 of surface area is required for bacterial nitrification of this ammonia. Given the biocarrier SSA of 500m3/m2, then 236l of biocarrier media will be required, in a vessel of 787l (at 30% fill). The MBBR in this system has been purposefully oversized to allow for future expansion of the aquaculture component. The MBBR is constructed from two 1m3 IBC tanks, each with a maximum fill volume of 800l. Thus, at maximum operating capacity, and a biocarrier fill rate increased to 60%, the MBBR could denitrify 480g TAN/day – equivalent to 16kg feed.
Figure 6: Completed MBBR chamber (left image) showing influent pipe (lower left of image), effluent pipe (top of image) and aeration grid (at the base of the chamber). Images on the right detail assembly of the aeration grid.
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Water enters and leaves the MBBR via 110mm pipe. Aeration is provided via 5 parallel 20mm PVC pipes, with 2mm holes drilled each 20mm along opposing sides, located at the bottom of each MBBR chamber. Water exits the MBBR via 110mm pipe to the aquaculture sump tank. Mineralisation Mineralisation is an aerobic, bacterial process by which the complex organic molecules found in solid wastes are broken down into simple mineral ions. Full mineralisation requires approximately 28 days of aerobic bacterial activity, thus a mineralisation tank must be large enough to allow a minimum 28-‐day residence time of discharged sludge. Sludge from the radial flow separator is discharged into a mineralisation tank – constructed in the same was as one of the MBBR chambers, from an IBC tank and aeration grid. Biocarrier media is added to the mineralisation tank to provide additional surface area for bacterial activity, and also to facilitate mechanical breakdown of larger particles through collision and agitation. The daily sludge discharge volume is around 20l (around 5l sludge is produced per 1kg feed), thus a minimum volume of 560l is required to provide the requisite 28-‐day residence time. The functional volume of the mineralisation tank is actually 800l, and so this requirement is exceeded in the current system design.
As fresh slurry is discharged into the mineralisation tank, the water level increases slightly and the supernatant overflows into a mineralised nutrient sump. The overflow is screened to prevent the exit of larger particles, and effluent passes through a 60μm filter before reaching the sump. The sump is fitted with a float-‐switch activated pump to deliver this nutrient laden water directly to the hydroponic system.
Figure 7: Mineralisation tank showing vigorous aeration (left) and screened pump chamber (right).
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Hydroponic component This system uses the hydroponic “Nutrient Film Technique” (NFT) for plant production. In NFT growing systems, plants are grown in tubes through which a thin film of nutrient rich water continually flows. The NFT component of this system consists of 80 6m long runs of 75mm diameter pipe, each pipe with a plant hole every 20cm; i.e. space for 2,400 plants.
NFT pipes are supported on custom-‐made iron stands, 1m in height and 4m in length. Four pipe stands are used to span the 6m NFT pipe run, and the stands are shaped to accommodate NFT pipes at densities of 5 pipes per meter (40 pipes) and 10 pipes per meter (40 pipes). Influent water overflows from the aquaculture sump tank and passes through a 60μm filter before going on to thy
hydroponic component. Water is delivered in a 25mm pipe mainline, and to each NFT pipe via individual 8mm flexible tubes with flow-‐control valves. Flow should remain in the region of 1-‐2l/minute in each NFT pipe. The NFT pipes are laid out to slope at around 1° -‐ 2° along their length, and they all drain to a common 110mm drainpipe which ends in a 1m3 sump tank. From this sump tank, water is pumped back to the aquaculture sump tank; the pumping rate into the aquaculture sump is equal to the overflow rate from the double sump to the hydroponic system. The desired overall flow rate is 1-‐2l/minute in each of the 80 NFT pipes; i.e. 80-‐160l/minute (4,800 – 9,600m3/h).
Figure 8: NFT pipes of the hydroponic system. Note flow control valve (left) and individual pipe supply lines fed by the 25mm mainline (right).
Figure 9: NFT pipe stands.
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Seedling production In addition to the NFT system for crop growout, the hydroponic component has three tables for seedling production. The tables’ tray-‐tops are sized to accommodate 9 standard seed trays – between 1683 and 3960 seedlings per table, depending on the hole size in the selected seedling trays. The seedling production tables operate on floating raft style basis, with the polystyrene seed trays floating on top of a constant depth of around 5cm water. The water flows continually in and out of the table’s tray top in order to ensure sufficient oxygenation and nutrient supply for vigorous seedling growth. Pumping and aeration The aquaculture system has been designed to be a low-‐head system. The maximum head (water surface level difference) between the fish tank water level and double sump water level is 20cm. Thus, it is possible to use an airlift system for water pumping. This has several advantages over using a water pump:
• Lower energy consumption for the volume of water moved • Lower maintenance as no moving parts are immersed in water • In addition to being pumped, water is also aerated – removing the need
for additional aeration in the fish tanks.
Figure 10: Seedling production table containing 9 260-‐hole polystyrene seedling trays.
Figure 11: Airlift system. Left image: water supply mainline and airlift bases. Centre image: Completed airlift assembly. Top right image: Air delivery manifold. Lower right images: Air injector and diffuser head.
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Airlift pumps can only raise water 20% of the insertion depth (the depth at which air is injected), and need airflow twice that of the desired water flow. In this system, each fish tank is supplied by its own airlift, however the four airlifts share a common water source, namely the outflow from the double sump. The water is delivered to the four airlifts through 110mm pipe. The airlift risers are 75mm in diameter, with air injection to a depth of 110cm via 20mm PVC pipe and a round air diffuser with 2mm pores. The airflow rate to each airlift must be maintained around 100l/minute (6m3/hour). In addition to the airlifts, aeration must also be supplied to the MBBR and mineralisation tank. All aeration requirements are met by one 2hp “Showfu” regenerative blower, operating continually. The hydroponic system is at a lower level than the aquaculture system. In this way, it may be gravity-‐fed from the double sump. However, this means that the head is too great to be able to use airlifts to return water to the double sump. As the total flow rate for the hydroponic system is comparatively low, then small submersible water pumps are used (two 150W Rio 5000 pumps). These pumps must also operate continually when the hydroponic system is fully stocked. However, during initial stocking it is possible to use only one pump and thus reduce electricity consumption.
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Management Cycling Prior to stocking the aquaculture system it is important to establish the bacterial communities in the biofilter. This can be achieved by suspending a mesh-‐bag of manure in one of the fish tanks, and switching on the pumps to operate the system. As the manure decomposes it releases ammonia (NH3/NH4+) – the primary metabolite excreted by fish. This ammonia provides a food supply to naturally occurring Nitrosomonas sp. bacteria and encourages their growth. Nitrosomonas consume ammonia, and produce nitrite (NO2-‐). The nitrite provides a food supply for Nitrobacter sp. Bacteria, which consume nitrite and produce nitrate (NO3+). By daily monitoring of water chemistry it is possible to check on the development of the bacterial communities; once ammonia and nitrite levels have spiked and returned to zero, and nitrate levels have started to rise, the system is ready to be stocked with fish. During cycling, and indeed until the aquaculture system is fully stocked, it is preferable to run the aquaculture and hydroponic systems independently. This is because until the aquaculture system is fully stocked, and feed is being given at the recommended rate, there will not be sufficient nutrient production to maintain the hydroponic system at full planting density. By operating the systems independently it is possible to supplement nutrients in the hydroponic system and thus fully plant it immediately. Aquaculture system The suggested management plan for the aquaculture system is for sequential batch harvests from each fish tank. The first fish tank is to be stocked with approximately 150 tilapia fingerlings. After 6 weeks the second fish tank is stocked with 150 quarantined tilapia fingerlings. After another 6 weeks, the third fish tank is stocked with 150 quarantined fingerlings, and after one more six-‐week period the first tank is fully harvested and re-‐stocked. In this way, a regular production of around 75kg fish per-‐harvest may be achieved. Preferable to a one-‐off batch harvest of each tank would be to gradually harvest the tank during its last month of growout; in this way the
Figure 12: A simple aquarium test for (from left) ammonia, nitrite and nitrate in the water.
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quantity of fish to be sold each day is reduced, and the remaining fish have chance to grow to a slightly larger size. Fish are to be fed at least three times per day. Each tank should be fed to satiation (the amount that the fish will consume within 5 minutes) at each feeding, taking care to never exceed the maximum daily feed amount of 1.5kg food per tank per day (or 6kg feed per day in the whole system). Periodically, a sample of fish should be netted from each tank and assessed for signs of disease or parasites. Hydroponic system The suggested management plan for the hydroponic system is to aim for daily (5 days per week) production of crops. Based on lettuce production, then 150 seedlings (5 NFT pipes) should therefore be harvested each day. Once 5 pipes have been harvested from the low-‐density planting section, all remaining pipes are advanced 5 spaces. 5 pipes are moved from the high-‐density stands to the low-‐density stands, and all remaining pipes in the low-‐density section are advanced 5 spaces. The harvested pipes are cleaned, and returned top the start of the low-‐density section, where they are re-‐filled with new transplants.
This system of management may be used either with purchased seedlings, or with seedlings produced on-‐site. If seedlings are to be produced on site, then it will be necessary to sow around 160 per day (to allow for lower than 100% germination rate) into the seedling production table. After three weeks, these seedlings will be ready to transplant to the growout system. When running individually, fertiliser should be added to the hydroponic system on a daily basis, to closely match the nitrogen loading that would be expected
Figure 13: Transplanting lettuce seedlings in the NFT pipes (left), and one week after transplanting (right).
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when operating the two systems in synchrony; i.e. equivalent to the amount of ammonia produced from regular feeding in the aquaculture system (maximum 176g TAN/day). When transplanting seedlings to the NFT pipes it is important to rinse off all soil from around the roots – this reduces the chance of waterlogging and the formation of anaerobic zones, reducing the opportunities for fungal attack of the plants. When using the seedling tables to produce seedlings, th planting holes should be filled with vermiculite only – no soil. This facilitates root rinsing (the vermiculite may be subsequently re-‐used), and reduces the opportunities for introduction of fine particulate matter into the system. Particulate matter provides a surface on which pathogenic fungi and bacteria may grow, and also necessitates more regular cleaning of the filter. Water quality During normal operation – the aquaculture and hydroponic systems operating together, the following water quality should be maintained: Ammonia: 0-‐0.25mg/l Nitrite: 0 mg/l Nitrate: 40-‐160mg/l pH: 6.8 KH: >50mg/l CaCO3 Temperature: 25-‐29°C When the systems are operating independently then the aquaculture system should be maintained as above. The hydroponic system will be relying on inorganic fertilisers, and so electrical conductivity (EC) of the water may be used to provide an indication of nutrient availability. Therefore, the hydroponic system should be maintained at pH 5.5-‐6.8 and EC 1200-‐1500μS.
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System operation Daily tasks
• Check all equipment (water and air pumps) is functioning, and flow-‐rates are correct.
• Check fish tanks – ensure fish are behaving normally • Check water pH – adjust if necessary • Feed fish • Drain sludge from radial flow separator • Harvest plants • Advance all NFT pipes • Transplant seedlings to cleared NFT pipes • Sow seeds to replace transplants • Clean hydroponic filter
Weekly tasks
• Full water analysis – test and record all parameters • Apply foliar feed to plants if necessary • Add chelated iron and other supplementary plant nutrients as necessary • Ensure seedling trays are fully planted • Net some fish for a visual health check
Monthly tasks
• Harvest and re-‐stock fish as necessary • Clean entire system, including pipework, air filter and air diffuser heads
in the airlifts.
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Troubleshooting Problem: Pumps not running. Check: That it is plugged in, and that the electricity cable is also connected to the mains. Check that there is not a power cut. If the pump is broken, buy a new one immediately. Problem: Plants not growing well, looking unhealthy; parasite infestation. Check: Apply foliar feed or aquaponics-‐safe pesticide if infestation is suspected. Test pH, ammonia, nitrite and nitrate levels. If nitrates are low, stock more fish or increase feeding. If pH is wrong, correct it. Problem: Fish looking unhealthy or dying. Solution: Test pH, ammonia, nitrite and nitrate – treat any water quality problems accordingly (see below). Visually inspect fish for parasites and treat accordingly. Problem: pH too high or too low. Check: Test KH, GH and pH. If pH is too high, add phosphoric acid each day until pH reaches 6.8-‐7.5, being careful not to change the pH by more than 0.2 points per day. If pH is too low, top up system with stored groundwater or add base such as CaO (lime). Problem: Ammonia or nitrites too high. Check: Check air pump and water pumps are working; check that the biofilter is not clogged or fouled, and that water is flowing normally. Stop feeding and remove uneaten food; test ammonia and nitrite every day till back to normal, resume feeding and continue testing the water for a couple of days more. Additionally you can exchange up to 50% of the water or harvest some fish. Problem: Nitrates too high. Check: Have plants been harvested/removed and not replaced? Transplant more seedlings to NFT pipes immediately; plant more seeds in seedling tray. Problem: Algae bloom – water turns green. Check: Ensure that the system is shaded from excess light. During an algae bloom it is common to get very low ammonia, nitrite and nitrate readings because the plankton takes up all available nutrients. By removing the light source, the plankton will die. Be vigilant for water quality problems, as a mass plankton die-‐off will liberate these nutrients and can cause very high ammonia levels. Plant more plants to take up available nutrients. Problem: Plants suffering from fungus. Solution: Increase flow rate in NFT pipes; increase slope in NFT pipes; increase aeration to sump tanks. If the hydroponic and aquaculture systems are being operated separately, discharge and replace water in hydroponic system.
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Directory Specialist aquaculture and aquaponic supplies LivinGreen, Hadera, Israel Manager: Moti Cohen Telephone: 0502999209 Email: [email protected] Aquaculture feed Raanan Feeds, Kfar Masaryk, Israel Contact: Omri Lev Telephone: 0508273018 Email: omri@raanan-‐fishfeed.com Plumbing and plastics Royalplas, Hebron, Palestine Contact: Monzer Zghier Telephone: 0599365041 Email: [email protected] Issa Habeeb store, Bethlehem Contact: Issa Habeeb Telephone: 0598046144
