Agri Kultuur March/ Maart 2016 - Page 23

Aquaponic Training Workshop should be viewed with a degree of caution because of different domestic market dependencies. Nonetheless, when addressing economic optimization, the three most important factors are: (1) sustainability considerations, which in the case of aquaponics, are interrelated with economic profits, since the reuse of resources should cut costs for the producer and for the customer; (2) technical optimization of processes (e.g., nutrient availability in different growth stages, nutrient recycling, etc.), and; (3) system components (e.g., design of the hydrological regime, P recycling unit, pH stabilizing reactors, etc.) System Design Considerations: Aquaponics system design and application can be considered a highly multidisciplinary approach drawing from environmental, mechanical and civil engineering design concepts as well as aquatic and plant related biology, biochemistry, and biotechnology. System specific measurements and control technologies also require knowledge of subjects related to the field of com- Aquaponica Research Basil in Aquaponic System puter science for automatic control systems. This high level of complexity necessarily demands in-depth knowledge and expertise of all involved fields. The design of aquaponic systems closely mirrors that of recirculating aquaculture systems in general with the addition of a hydroponic component and the possible elimination of a separate biofilter and devices (foam fractionators) for fine and dissolved solids removal. Fine solids and dissolved organic matter generally do not reach levels that require foam fractionation in aquaponic systems at the recommended design ratio. The essential elements of an aquaponic system consist of a fish rearing tank, a settle able and suspended solids removal component, a biofilter, a hydroponic component and a sump. Component Ratios: Aquaponic systems are generally designed to meet the size requirements for solids removal (for those systems requiring solids removal) and biofiltration (if a separate biofilter is used) for the amount of fish Tilapia Fish in Aquaponic System Aquaponic Farmer being kept. After the size requirements are calculated, it is prudent to add excess capacity as a safety margin. However, if a separate biofilter is used, the hydroponic component is the safety factor because a significant amount of ammonia uptake and nitrification will occur regardless of hydroponic technique. Another key design criterion is the ratio between the fish rearing and hydroponic components. The key aspect of the criterion is the ratio of daily feed input to plant growing area. If the ratio of daily feeding rate to plant growing area is too high, nutrient salts will accumulate rapidly and may reach phytotoxic levels. Higher water exchange rates will be required to prevent excessive nutrient build-up. If the ratio of daily feeding rate to plants is too low, plants will develop nutrient deficiencies and more nutrient supplementation will be required. The optimum ratio of daily fish feed input to plant growing area will max imize plant production while maintaining relatively stable levels of dissolved nutrients. A volume NFT System