ENGINEERING DESIGN CONSIDERATIONS FOR RECIRCULATING AQUAPONICS SYSTEMS (RAqS) TO MAXIMIZE PRODUCTIVITY AND ECONOMIC VIABILITY.  

Todd C. Guerdat*, James M. Ebeling
University of New Hampshire, Durham, NH, USA
todd.guerdat@unh.edu

The recent and growing interest in aquaponic culture, where dissolved fish wastes (e.g. nitrogen, phosphorous potassium) provide the nutrients necessary for plant growth in a shared recirculating system, has brought about a menagerie of design concepts with vastly varying results. Additionally, many commercial aquaponic operations focus on growing lettuce and tilapia because both are relatively easy to culture and limited research has been conducted on other species under aquaponic production settings. For commercial aquaponic production to be profitable, it is essential that high-value crops (fish and plants) be co-cultured optimally, energy inputs reduced, and engineered system designs focus on logical and practical process integration.

The current limited availability of 'engineered' aquaponic systems reflects in many ways the historical development of intensive recirculating aquaculture system design. Most of the earlier aquaculture systems utilize the simplest and most basic water treatment systems reflecting the designer's vast knowledge of hydroponics, but limited knowledge of aquaculture. There are several areas where good engineering design can have a significant impact on the economic viability of an aquaponic system. From an engineering design perspective, challenges such as system designs correctly sizing the fish and plant production goals, balancing of differing water quality operating conditions (e.g. pH), efficient nutrient utilization, and effluent management.

As a means for balancing the needs of both the fish and plant systems, system designs utilizing both coupled and decoupled aquaponic approaches have been implemented. Coupled designs have many different rationales such as reduced costs and operating expenses, while decoupled systems boast increased plant production. Research on the means for system integration and characterizations of the aquaponic implementations in use today is needed.

The University of New Hampshire's Agricultural Experiment Station (NHAES) has a new agricultural engineering research program which will include aquaculture, aquaponics, energy and nutrient utilization efficiency, and agriculture production and waste management. Immediate research is first focusing on engineered recirculating aquaponic system (RAqS) operating conditions by investigating the plant and fish growth rates in three different culture conditions: separate hydroponic and recirculating aquaculture systems, coupled aquaponic systems, and decoupled aquaponic systems. The specific objectives are to: 1) Construct the three different production systems in triplicate, 2) Conduct growout trials to validate system performance in terms of water quality, growth rates, feed conversion ratios for fish and plants. Growth rates, feed conversion of fish and plant production will be quantified in each of the systems, 3) Investigate nutrient utilization efficiency through determination of specific plant nutrient uptake rates as well as plant tissue nutritional analysis, and 4) Develop a refined RAqS production system design based on the data collected.

Research system designs will be explained and project progress will be reported as appropriate at the time of the presentation.