NUTRIENT DYNAMICS AND MANAGEMENT IN AQUAPONICS WITH TILAPIA AND CATFISH Tommaso Danelli1 , Gino Smit2 , Jan Schutte2 1. Registered Agronomist Doctor; 2. Youmanitas Energy Farms Abstract This paper describes the research developed during “Aquaponics Inside Out" project, which intended to investigate the use of different plant and fish species and the efficiency of a set up consisted of a separate space for fish breeding and plants. Different parties were involved to gather knowledge and expertise on various disciplines and to generate a valuable know how for aquaponics design and management. Monitoring water quality with an analytical approach aimed to create tools for production of both fishes and vegetables in optimum conditions, reducing employment of antibiotics and pesticides. This paper presents different tools for design and management of a recirculating aquaponic system: a model that can be implemented with all the typical elements of aquaponics, indications for monitoring nutrients in the water and plant composition; considerations about effect of fish choice on nutrient solution. Introduction Aquaponics is the integrated cultivation of plants in an aquaculture system [1], wherein the fish water tank enriched with nutrients is used for plant growth. Its role for food security would be particularly relevant because the global population is expected to reach 9.6 billion around 2050 with more than 75% living in urban areas [2]. Urban population growth will require an increasing demand for animal protein [3] and in this context, conventional farming meets resource limitations, decrease of arable surfaces, constrained freshwater supplies, soil degradation and soil nutrient depletion [4,5]. This alerts researchers to the necessity to compensate existing sustainability deficits in agricultural food systems. Considering the EU directive 2000/60/EC of 23rd Oct 2000, this necessity is perceived also in the aquaculture sector, where there is a call is for environmental friendly aquaculture production systems. Combining aquaculture to hydroponics in aquaponics provides an efficient mineral nutrient recycling and a reduced water use by recirculation [6]. Although preliminary research has shown that developed aquaponic system components are not yet fully realized in view of either cost effectiveness or technical capabilities [7,8], the aquaponics concept is promising to contribute to both global and urban sustainable food production and should at the same time diminish pollution and need for resources. Validation of aquaponics as a sustainable food production alternative is still a open challenge, considering the aim of fully controlled and standardized aquaponic systems that will be easy to handle and economically viable and competitive. To reach this goal, there are some improvements that need to be addressed. This includes: an improved nutrient solubilization and recovery to reduce extramineral addition, limitation for need of water exchange, use of alternative energy sources and methods for pH stabilization. Many research institutes and companies are trying to fill the knowledge gap present in the design of a sustainable and competitive aquaponic system. One of the first Dutch research projects on aquaponics was led by Eco Futura (EF) in 20072008, it proved the technical and economical feasibility of linking tilapia farming and tomato horticulture. This paper describes the research developed during “Aquaponics Inside Out" (APIO) project, which intended to investigate the use of different plant and fish species and the efficiency of a set up consisted of a separate space for fish breeding and plants. Different parties were involved to gather knowledge and expertise on various disciplines and to generate a valuable know how for aquaponics design and management. Monitoring water quality with an analytical approach aimed to create tools for production of both fishes and vegetables in optimum conditions, reducing employment of antibiotics and pesticides. The project took place in Rotterdam Metropolitan Area, on the premises of the restaurant and urban farm “Uit Je Eigen Stad”. Location choice pursued the objective of reducing the carbon footprint, in the frame of local urban farming production. Finally, the products were sold and consumed in the onsite restaurant, in a variety of dishes and recipes. Furthermore, this choice improved the economical performance and financial viability of the project. Students from different education entities participated in this project, generating a strategic disclosure of knowledge and innovation toward the community. On the other hand, setting a production line in an old building, by the employment of labour with no expertise had been a challenge, but also an attained result in the project management. Material and methods Fig. 1: General systems scheme: A. trickling bed filters; B. fish basin; C. fish feeder; D. sieve filter; E. and F. fertilization tank and nutrient stock (not used); G. plant basin; E. pump. Location for the system set up was a conjoined space obtained in two buildings: a former railroad warehouse of 250 m2 situated on upper floor and a greenhouse situated between the two walls of the adjacent buildings at the ground floor. The experimentation considered in two separate aquaponic systems; one for Tilapia niloticus and one for African catfish Clarias gariepinus . The set up for Aquaponics resembled the design of a traditional Recirculation Aquaculture System (RAS) and a Deep Water Culture (DWC) technology. Each system consisted of different fish containers, one plants growing basin, trickling bed filters, a sediment tanks, water tubes for inflow water, sewage system for drainage, heating elements and UV sterilizing units. Whole water volume was 61 m3 for Catfish system and 68 m3 for Tilapia system and source . The fish basins for both system were positioned at the second floor. This difference in height allowed the installation at the ground floor of just one flow circulation pump for each system. Catfish fish basin was obtained from 5 large PE tanks and 8 IBC containers, for a total volume of 9,8 m3 . Tilapia fish basin was realized with 8 IBC tanks and 20 glass acquariums, for a total water volume of 20,4 m3 . Each container had his own stand pipe to regulate water volume. Fish density were held at extensive breeding values: Tilapia at 80 kg/m3 and Catfish at 200 kg/m3 . Fishes of both systems were fed twice a day with commercial pelleted feed. Each plant basin measured 120 m2 and had total water volume of 150.000 liters. The support for plant growth were floating PE rafts with on top PVC cones, with density of 25 m2 . Plant material consisted in coconut fiber rooted seedlings of the following species: Lollo Bionda, Lollo Rossa, Lollo TRIO, Paksoi, Bibb lettuce, Ruccola, Watercress ( Rorippa nastur ), Romain Lettuce (Palosta, Secco, Sadawi). Heating source for the water was the existing gas heater of the building, used to maintain constant water temperature of 25 ± 1 °C, optimum for the chosen warm water fish species. Oxygen was suppleted in the plant basin by a Venturi pump system. Water and plant composition analysis were outsourced and conducted by Groen Agrocontrol facilities in Delfgauw. Two water sources have been used during experimentation: a 20 m3 basin of surface water and ground water obtained by installation GH pump on the ground. The analytical approach of this study was possible with the contribution of all parties involved, in particular for outsourcing the development of an aquaponic flow simulation model APIO, for nutrient solutions and source water analysis and for the standards about quality of plant products composition. Fig. 2: Water analysis of source water used in the experimentation. Results Flows calculation obtained with APIO model, for fish tanks in tilapia system, gave the following results: input as fish food was 271,43 kg N tot; output as fish production 75,27 kg N tot. Total nitrogen balance for the fish tank was a positive 196,16 kg N toward the system. Fish production entailed a water tot consumption of 584,3 l of water from different sources. Statistical analysis on water content in catfish and tilapia systems by mean comparison with Fisher test ( p value < 0,05) marks a significant effect of fish choice on NO and Zn concentrations in the nutrient 3 solution. Catfish system water contained NO3 7,47 ± 0,6 mmol/l and Zn 15,87 ± 0,81 mmol/l. Tilapia system water revealed a lower amount of those nutrients, with NO 0,75 ± 0,91 mmol/l and Zn 0,6 ± 0,7 3 mmol/l. Further analysis with lower level of significancy ( p value < 0,10) suggest an effect also on pH, K+ , 2+ Ca water content depending on fish choice. Statistical values for the two systems were: pH 5,8 ± 0,14 for catfish and pH 9,07 ± 0,42 for tilapia; K+ 0,9 ± 0,14 mmol/l for catfish and K+ 0,47 ± 0,1 mmol/l for tilapia; Ca2+ 3,25 ± 0,49 mmol/l for catfish and Ca2+ 1,5 ± 0,56 mmol/l for tilapia. A scarcity of Fe (< 0,05 mmol/l) has been registered for both systems. Fig. 3: Normalized parameters of Catfish and Tilapia systems nutrient solution, based on the target values + and concentrations for Lettuce cultivation in the systems: EC 2,6 mS/cm; pH 5,5; NH 4 1,25 mmol/l; NO 3 3 + 2+ 2+ 2 19 mmol/l; PO 11 mmol/l; Ca 4,5 mmol/l; Mg 1 mmol/l; SO 4 2 mmol/l; K 4 1.125 mmol/l; Fe 15 μmol/l. Dry mass composition of plants cultivated in the Catfish system exhibited no significant difference among different plant species ( p value > 0,05). Nutritional condition of has been assessed by aggregation of measurements for the different plant species. Sufficient level has been determined for the following 3 2+ nutrients: N 461 ± 180 mmol/kg DM; Mg2+ tot 3091 ± 609 mmol/kg DM; PO 4 232 ± 34 mmol/kg DM; Ca 248 ± 42 mmol/kg DM; B 3,2 ± 0,73 mmol/kg DM; Cu 168 ± 69 mmol/kg DM; Mn 7,7 ± 4,5 mmol/kg DM; Zn 18,7 ± 3,7 mmol/kg DM. Content of microelements Mn and Zn is, respectively, 4 times and 21 times the expected values of Mn 2 mmol/kg DM and Zn 0,85 mmol/kg DM. Deficiencies have been revealed for K+ 1082 ± 330 mmol/kg DM and Fe 1,7 ± 0,45 mmol/kg DM. Fig. 4: Normalized plants composition grown in Catfish system, based on optimum growth condition for 3 + plants in the system: N 2750 mmol/kg DM; Ca2+ 250 tot 3500 mmol/kg DM; PO 4 225 mmol/kg DM; K 2+ mmol/kg DM; Mg 200 mmol/kg DM; Fe 3,5 mmol/kg DM; B 3,5 mmol/kg DM; Cu 175 mmol/kg DM Discussion Since the APIO model was in early development stage the complete simulation of nitrogen flows inside the system was not possible. Nevertheless, the model determined the precise amount of nitrogen introduced by fish farming management in the tilapia system. This result was possible only on a basis of source water monitoring and controlled feeding material. As a starting point, it had been decisive to determine the correct system design and dimensions. Fish farming management imply also a consistent water consumption. This consideration should be always taken in account while designing aquaponics system with aims on water preservation. As the plant growth simulation was not yet implemented in APIO model, the complete water balance in the system is not available. The complexity of modeling complete nutrients dynamics in the aquaponic water solution makes more viable, for practical intervention, the analytical approach based on measures and monitoring. Systems water analysis delivered important elements to evaluate effects of fish farming on the nutrient solution quality. The nutrient solution deficits suggested a possible fertilization with a custom formulation of N P K Ca S Fe, to avoid plant stress for deficiencies. The significant higher level in catfish nutrient solution of NO and Zn 3 suggest that this species has a better capability than tilapia to maintain these nutrients in an aquaponic recirculating system. As a further consideration, it is possible that the two fishes generate different + + wastewaters with different NO3 /NH4 ratio. Since NH4 is continuously nitrificated in a correct aquaponic design, NO3 can be a more reliable parameter to be measured to evaluate the amount of nitrogen in the solution and water quality for plants. Effects on concentrations of K+ , Ca2+ have lower significancy, maybe caused by the small sample size of only three measures. Different values of pH can be imputable on the fishes choice, and this would have a massive impact in aquaponic systems design, since tilapia shown levels of pH not suitable for plant production. An increasing in pH can be generated by algae proliferation. An important factor that influences algae growth is the presence of nitrogen in either NO3 + or NH ions. This consideration increases the importance of the results obtained on NO concentration 4 3 in the catfish water. On plant composition, some results were expected if considering nutrient solution deficits exhibited in both the systems. Conclusions The presented project provided different tools for design and management of a recirculating aquaponic system: a model that can be implemented with all the typical elements of aquaponics, indications for monitoring nutrients in the water and plant composition; considerations about effect of fish choice on nutrient solution. Acknowledgements “ Aquaponics Inside Out project", initiated by Uit Je Eigen Stad, project partners are Youmanitas Energy Farms, Tauw Engineering, Proeftuin Zwaagdijk and Groen Agrocontrol. Funded by Dutch Ministry of Economic Affairs, Agriculture and Innovation (EL&I) and European Maritime and Fisheries Fund (EMFF). References 1) Rakocy, J.E. Island Perspectives; Virgin Islands agricultural Experiment Station: Saint Croix, VI, USA, 1989; pp. 5–10. 2) UN. Human development report 2013. Available online: http://hdr.undp.org/en/media/HDR_ 2013_EN_complete.pdf (accessed on 13 August 2014). 3) Alexandratos, N.; Bruinsma, J. WORLD AGRICULTURE TOWARDS 2030/2050: The 2012 Revision ; FAO, Agricultural Development Economics Division: Rome, Italy, 2012. 4) Bindraban, P.S.; van der Velde, M.; Ye, L.; van den Berg, M.; Materechera, S.; Kiba, D.I.; Tamene, L.; Ragnarsdottir, K.V.; Jongschaap, R.; Hoogmoed, M.; et al . Assessing the impact of soil degradation on food production. Curr. Opin. Environ. Sustain. 2012 , 4 , 478–488. 5) Klinger, D.; Naylor, R. Searching for Solutions in Aquaculture: Charting a Sustainable Course. Annu. Rev. Environ. Resour. 2012 , 37 , 247–276. 6) Turcios, A.E.; Papenbrock, J. Sustainable Treatment of Aquaculture EffluentsWhat Can We Learn from the Past for the Future? Sustainability 2014 , 6 , 836–856. 7) Rakocy, J.E. Aquaponics—Integrating Fish and Plant Culture ; WileyBlackwell: Hoboken, NJ, USA, 2012; pp. 344–386. 8) Vermeulen, T.; Kamstra, A. The need for systems design for robust aquaponic systems in the urban environment. 2013 , 1004 , 71–78.
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