The successful completion of this project was achieved using a multi-disciplinary approach in the design, testing, and implementation of a re-circulating integrated aquaculture production system. Graduate students were individually selected for this project based on their expertise in soil, water, and the environment, and their ability to carry out research and planning towards the solution of environmental and resource use problems.

 

The first objective was completed by developing a large-scale re-circulating integrated aquaculture system in which aquaculture effluent was used to irrigate individually potted plants (Fig. 1). Three independent RIAA systems were set up to allow for experimental testing. In each system, water from a 5000 L doughboy swimming pool was delivered to 300 individually potted plants using a surface drip irrigation system. The pots were placed into 30 meter long aluminum metal channels which were built at a negative 2° slope. Thus, after being delivered to each pot, water percolated through the soil, migrated down the channels of the plant troughs, where it was collected in basins located at the terminal end. From there, water was pumped back into the fish tanks.

 

The second objective was completed by performing successive experiments to identify the conditions which promote economically viable and environmentally sound food production. Data were analyzed to determine which systems generated high plant and animal yield production, maximum nutrient utilization, and high benefit to cost to ratios. A total of three plant species were grown using aquaculture effluent as nutrient laden water source; barley (Hordeum vulgare), basil (Ocimum basilicum), and soybean (Glycine max). Each of these plant species was supplied with aquaculture effluent from pools containing Tilapia at densities of 3 kg/m3, 6 kg/m3, and 9 kg/m3 respectively. Total fish feed and fish density was kept constant over the course of each experiment to ensure the same nutrient load was being delivered to each system over time. The number of plants was maintained the same for all experiments at 300 plants for each system. 150 plants were grown in ½ gallon pots and 150 in 1 gallon pots to evaluate amount of soil needed for efficient growth. The efficiency of nutrient utilization and net nutrient uptake in each integrated aquaculture system were determined. Water samples were extracted for water quality analysis both before it enters and after it exits the plant beds. Nitrate, ammonia, total nitrogen, phosphate and orthophosphate concentrations were determined from each of water samples. Temperature and dissolved oxygen were also monitored in each system. Nutrient uptake efficiency was calculated as the difference between nutrient concentrations contained in the influent and effluent water samples. Water quality and plant growth rates were compared over time to determine the conditions which maximized plant and animal biomass production through nutrient utilization.

 

One of the key findings in part of the second object was that all plant species were able to grow readily using aquaculture effluent as a form of fertilizer. However, the growth rates of barley, basil, and soybeans, were dependent upon the nutrient concentrations in the water as well as the size of the pots in which the plants were grown. Moreover, the nutrient concentrations in the aquaculture effluent were proportional to the density of fish in the 5000 L pools (i.e. higher densities of fish correlated to higher nutrient concentrations). Total plant height was consecutively higher from treatments with 3, 6, and 9 kg of Tilapia per m3. In terms of rapid plant growth, the best results were obtained by irrigating plants with aquaculture effluent from the pools with 9 kg of fish per m3. This was the highest density of fish used in this project studies and it is reasonable to assume that higher plant yields would be generated using irrigation water from aquaculture tanks with densities of fish greater than 9 kg per m3. Similar results were found for each plant species was collected from each experiment.

 

Approximately 80% of the total nutrients were removed through the irrigation process, irrespective of the initial concentrations, as the effluent migrated through the potted soil. The hypothesis prior to the start of the experiment was that a reduction in nutrient concentration would be observed over time in correlation to plant growth. However, in the experiment, no such correlation was observed. In contrast, the soil was observed to act as a physical filter which 80% of the organic nutrient load (presumably bound to algae and other micro biological species) was captured as the irrigation water migrated through the soil. The final significant result observed in this project was that approximately 90% of the aquaculture effluent was recaptured and pumped back into the pools. 10% was presumably lost primarily through evaporation. System leaks were occasionally found and fixed on site and the associated water loss was not considered significant.

 

The final objective of the P3 Phase I project was completed by disseminating results to the local community, the academic community, NGOs, and farmers both in the United States and several countries around the world including Uganda, Mexico, and Paraguay. In support of the RIAA project, a study was completed on the potential economic impacts of aquaculture development in rural communities. This work, titled “The Use of Multipliers to predict the effect of growth of aquaculture on rural Arizona Communities,” was presented at the World Aquaculture Society Conference in Busan, Korea in May of 2008. Results from the project will also be presented at an upcoming conference in May, 2009. The title of this up-coming presentation is “Utilizing aquaculture effluent from Tilapia to grow Barley (Hordeum vulgare) using RIAA systems.” A manuscript is also is being generated in combination with this presentation and will be submitted to the Journal of Aquaculture in the summer of 2009.

 

Students from the project developed partnerships with three high schools in Tucson, Arizona. The graduate students traveled to the local schools and held public seminars and class room discussions emphasizing sustainable agriculture methods. Students from the high schools also traveled to the Environmental Research Lab (ERL), where development of the RIAA systems took place, as part of class room field trips.

Hide Additional Record Data

Keywords:

HUMAN HEALTH, WASTE REDUCTION, INTERNATIONAL COOPERATION, SUSTAINABLE ENVIRONMENT, DESIGN OPTIMIZATION, ENVIRONMENTAL EDUCATION, ECOLOGICAL DESIGN,