Progress 10/01/07 to 09/30/08
OUTPUTS: Biofloc experiments were conducted using bioreactors to treat tilapia effluent with and without carbon supplementation. Additionally, biofloc generated in bioreactors using sugar and tilapia wastewater was used as a component of three formulated, nutritionally-complete shrimp diets. Three diets containing biofloc were compared against two control diets which did not include bioflocs. The five diets were compared in growth and survival trials. This work has been presented at two conferences, Aquaculture America (Orlando, Florida, February 2008) and the International Recirculating Aquaculture Conference (Roanoke, Virginia, July 2008). Water quality data were collected at Virginia Shrimp Farms (VSF) to assure adequate water quality conditions and mixing for the production of shrimp under variable stocking densities. To analyze the operation and efficiency of the treatment devices on the shrimp grow out system at VSF, sample ports were placed to capture the influent and effluent from each step of the treatment process. Four rounds of sampling were completed between May 21 and July 14, 2008. The analyses included measurements of pH, temperature, salinity, dissolved oxygen, ammonia, nitrite, nitrate, orthophosphate, total organic carbon, total suspended solids, and alkalinity. Through this monitoring, mixing conditions in the production tanks were evaluated by performing depth sampling at multiple locations within the same tank. Analysis of the data shows that the mixing within the tanks is adequate as evidenced by nearly identical water quality measurements obtained at different depths and locations within a given tank. A horizontal substrate with either 12, 18 or 24 vertical inches between layers was placed in each shrimp growout tank at VSF. Each of the nine commercial growout tanks at VSF received one of the substrate treatments, resulting in 3 replicates. Twice weekly for 25 weeks, shrimp were netted by hand, counted and weighted. Using this data, growth rate for each tank and each substrate configuration was plotted. Shipping studies were conducted to determine the survival rate of Litopenaeus vannamei when shipped either dry or in water. For the dry shipping study, shrimp were acclimated from the growout temperature of 30C to shipping temperature of 9, 12 or 15C at three different acclimation rates. Following acclimation, shrimp were placed in a box lined with a plastic bag which contained wet excellsor and the bag was filled with oxygen and then sealed. The boxes where stored in incubators maintained at 9, 12 or 15C and opened after 24 hrs to determine survival rates. In the wet shipping studies, shrimp were acclimated from 30 to 21, 19 or 17C in a period of two to four hours and then placed in water of the same temperature and trucked from Virginia to New York City, New York, where survival was noted (approximately 20 hours in transit before unloading). PARTICIPANTS: Dr. George Flick provided oversight for the project and directed the live shrimp shipping studies. Dr. Lori Marsh conducted the substrate research. Dr. David Kuhn conducted the biofloc research. Dr. Gregory Boardman provided assistance for water quality assessment and treatment issues. Mr. Todd Blacher was responsible for the day-to-day management of the shrimp facility. Dr. Stephen Smith provided veterinary medical advice as needed. Amy Cheatham and Susan Mirlohi collected water samples and ran water quality analyses. Dianne Bourne and Sheila Holliman performed microbiological testing. Partner organizations and collaborators included Zeigler Brothers, Inc., MeriCal, Blue Ridge Aquaculture, Virginia Shrimp Farms, and Texas A&M University. Training or professional development: Two International conferences were conducted in July, 2008--The Aquaculture Engineering Society forum and the International Conference on Recirculating Aquaculture. The two programs brought international experts together to discuss recent advances in the scientific and technological aspects of recirculating aquaculture. Some of the information presented at both programs was obtained from research activities that occurred in this project. Attendees included scientist, regulators, and entrepreneurs, having substantial financial investments in recirculating aquaculture systems. TARGET AUDIENCES: The target audience for this work is anyone currently operating or considering starting an indoor recirculating aquaculture venture. In addition to specific research carried out with commercial scale shrimp production systems, a video describing indoor recirculating aquaculture was produced and distributed at the Boston Seafood Show. PROJECT MODIFICATIONS: Not relevant to this project.
Bioflocs were generated in sequencing batch reactors (SBRs) using wastewater discharged from an indoor recirculating aquaculture facility producing tilapia. Treatment efficiencies and biofloc production were enhanced when carbon supplementation was used compared to no carbon supplementation. Biofloc yield averaged 0.7kg of biofloc per 1 kg of sugar and removal of reduced nitrogen and dissolved organic matter exceeded 85%. The resulting biofloc had an average crude protein content of 49 (g/100g dry matter) compared to a crude protein content of 14(g/100g dry matter) for untreated solids removed by drum filter from the same wastewater stream. Five shrimp diets were formulated with equivalent levels of crude protein (35.0%), crude fat (7.5%), crude fiber (3.25%), calcium (2.75%), magnesium (1.00%), phosphorus (1.90%), potassium (1.30%), and sodium (0.90%). Two of the diets contained no bioflocs, in two of the diets, soybean isolate was replaced by biofloc at inclusion levels of 7.8 and 15.6% biofloc; in one diet, fishmeal was replaced with bioflocs at 7.8% and fish oil was added at 0.50%. Final survival rates in the growth trials were not statistically different for the various diets. However, diets that contained bioflocs resulted in significantly increased growth rates compared to diets without bioflocs. However, there were no significant differences in growth rates within the three diets that contained bioflocs or within the two diets that did not contain bioflocs. The results of this study are encouraging. Significant enhancement of shrimp growth was observed for biofloc diets over the control diets, irrespective of biofloc inclusion levels or replacement of soybean versus fishmeal protein. This project demonstrates the feasibility of treating one aquaculture wastewater while producing a quality ingredient for shrimp feed--a novel approach that could increase economic and environmental sustainability of clear water recirculating aquaculture systems. Several organizations expressed an interest in expanding the study and potentially commercializing the process. A multi-disciplinary, multi-organization research group, including two universities, three commercial aquaculture firms, and a feed manufacturer has formed. This public/private partnership is expanding the scientific and technological activities outlined in this research activity. There was no discernible difference in shrimp growth rate as a function of substrate spacing in the growout tanks. There were no significant differences between the three acclimation rates or the three storage temperatures in the dry shipping study. Survival was unacceptably low for all treatments (below 30%), indicating that more study is needed to find an acceptable dry shipping method. Live shipping trials had survival rates from 87 to 96%. There was a trend in the data showing greater survival with a shorter acclimation period (2 versus 4 hours) and when shipping occurs at cooler temperatures (17 versus 21 C). The ability to ship live animals with high survival rates (above 90%) opens up a high-value market for shrimp produced in recirculating aquaculture systems.
- Kuhn, D.D., G.D. Boardman, A. Lawrence, L. Marsh, G.J. Flick, Jr. 2008. Use of Bioflocs as an Ingredient in Shrimp Feed. In: Proceedings of the 7th International Conference on Recirculating Aquaculture. July 25-27, 2008, Roanoke, Virginia. pp. 74-78.
- Marsh, L., Flick, G., Boardman, G., Kuhn, D., and Smith, S. 2008. Collaborative research toward a sustainable shrimp aquaculture industry in Virginia. In: Proceedings of the 7th International Conference on Recirculating Aquaculture. July 25-27, 2008, Roanoke, Virginia. pg. 518.
- Kuhn, D.D., G.D. Boardman, S.R. Craig, E. McLean, and G.J. Flick, Jr. 2008. Integrating tilapia effluent with shrimp culture to enhance aquacultural sustainability. Aquaculture America 2008. February 9-12, 2008, Lake Buena Vista, Florida.