Location: Cool and Cold Water Aquaculture Research
2019 Annual Report
Objectives
Objective 1. Develop technically advanced, environmentally compatible, and sustainable closed production systems and techniques
Sub-objective 1.1 Optimize the cost and effectiveness of technologies to remove nitrogen and phosphorus from recirculating aquaculture systems and their effluent.
a) Optimize system water quality and evaluate salmonid performance when using membrane biological reactors to digest biosolids, remove nitrate, and practically eliminate water flushing requirements in each water recirculating system module.
b) Evaluate effectiveness of woodchip bioreactors for treating the effluent from water recirculating systems.
Sub-objective 1.2 Increase the energy efficiency of CO2 degassing technologies.
Sub-objective 1.3 Use refinements in water treatment process design and economies of scale to decrease the capital cost required per tonne of fish produced within water recirculating systems.
Objective 2: Improve salmonid performance, health and well-being in land-based systems through research on nutrition, rearing environment, and control of pathogens and fin erosion.
Sub-objective 2.1 Field-test rainbow trout germplasm resources when reared to 2kg harvest size within intensive water reuse systems and ID top performing individuals and families.
Sub-objective 2.2 Compare the effects of alternate protein (zero fish meal) versus fishmeal-based diets on growth performance and welfare of select families of Troutlodge rainbow trout when reared to 2 kg. We will also measure water quality, water treatment process performance, and waste production rates in recirculating aquaculture systems operated at low flushing rates.
Sub-objective 2.3 Identify strategies to minimize losses of Atlantic salmon smolt to Saprolegnia infections following vaccination in water recirculating systems.
Approach
The ability to provide U.S. consumers with high-quality, sustainably-produced seafood hinges upon research that supports increased domestic aquaculture production and the development of new and improved technologies. This proposed work encompasses several USDA ARS Action Plan components, primarily technology development for sustainable production systems (Component 4), alternative protein
investigation (Component 2), and disease prevention (Component 3). The first objective, which is focused on recirculating aquaculture system (WRAS) technology development, will investigate two water qualityimprovement technologies: (1) low-cost woodchip bioreactors for nitrate removal from aquaculture effluents, and (2) membrane biological reactors that produce a clean filtrate for reuse in the WRAS, which eliminates makeup water flushing and the point-source discharge. Refinement of water treatment processes and use of economies of scale to reduce capital costs of WRAS will also be a key focus. This
work will also investigate a new and potentially more energy efficient and cost-effective carbon dioxide stripping technology. Within the second overarching objective, we will evaluate the performance of commercially available rainbow trout strains (fingerling to 2 kg) cultured in WRAS, and will identify
strategies to minimize Saprolegnia infections in Atlantic salmon smolt cultured in WRAS after vaccinations. In addition, pressing societal concerns about the sustainability of fish feed and the rising cost of fish meal provide the emphasis to compare the effects of alternate protein (zero fish meal) and
fishmeal-based feed formulations on trout health and performance, waste production, and water quality. Through this work plan, we are eager to support the USDA in their forward-thinking efforts.
Progress Report
This project was developed with the overall goal of refining technologies that will enhance the sustainability of the domestic aquaculture industry while reducing its impacts on the environment. We have made substantial progress towards achieving this goal, and these results are described for each of the Project Plan objectives:
Sub-Objective 1.1a: We previously reported that membrane biological reactors (MBRs), integrated as unit processes within recirculating aquaculture systems (RAS), are able to digest biosolids produced by fish and remove nitrate, which eliminates makeup water flushing requirements and point-source discharge, and allows for greater flexibility in siting and permitting RAS fish farms. Ongoing data analyses have revealed that on average, RAS with MBRs required six and a half times less makeup water, although a range of water quality concentrations were significantly greater in these systems (chloride, carbon dioxide, heterotrophic bacteria count, pH, nitrate-nitrogen, total ammonia-nitrogen, total phosphorous, and true color, as well as dissolved concentrations of calcium, copper, magnesium, and sulfur). These culture environment differences did not affect rainbow trout growth, feed conversion, or survival. Additionally, concentrations of common off-flavors (geosmin and 2-methylisoborneol) in water and fish flesh were not affected by MBR presence. Overall, incorporating MBRs within RAS results in substantial water savings and, based on our research, appears to be biologically feasible for RAS rainbow trout production.
Sub-Objective 1.1b: Since FY2017 we have evaluated relatively low-tech and inexpensive woodchip bioreactors (i.e., trenches filled with woodchips that fuel heterotrophic bacteria that, in turn, remove nitrate nitrogen, phosphorus, and suspended solids from aquaculture effluent). We have previously observed that relatively high levels of suspended solids in certain aquaculture effluents can create plugging and hydraulic problems in woodchip bioreactors operated over extended periods or at short hydraulic retention times. We have therefore evaluated improved flow distribution to determine treatment efficiency and deviation in hydraulic grade line due to plugging after long-term operation. Monitoring the hydraulic grade line in influent distribution manifolds demonstrated that, over time, water takes longer to enter the system, an indication of cumulative clogging around inlet manifolds. Woodchips sampled from bioreactors demonstrated increasing phosphorus content over time, particularly on samples pulled from the bottom of systems, confirming the high solids removal was the primary driver for phosphorus reduction but also created a greater risk for mineralization. The carbon to nitrogen ratio found in woodchips after 267 days of operation also indicated that decreases in the ratio over time were not significant. The extent of biologically driven nitrogen removal depends on both system hydraulic retention time and water temperature, where increased transit time and temperature lead to the highest nitrogen removal. We determined that removal rates must be carefully balanced with removal efficiencies, as a 100% removal efficiency can lead to other detrimental reduction processes. Our woodchip bioreactor design, with a 24 hour hydraulic retention time, balanced both removal metrics, and could likely fit easily into an aquaculture operation’s daily schedule.
Sub-Objective 2.1: We previously reported that, among tested rainbow trout genetic strains, there are significant differences in growth performance when raised in a partial water reuse system up to a harvest size of 2 kg. We have continued our research examining different strains (and ploidy) of salmonids in RAS, and plan to evaluate both rainbow trout (steelhead) and Atlantic salmon strains over the next five years as they are raised in our semi-commercial scale RAS up to a harvest size of 4 kg. Continued research in this area will provide stakeholders with critical performance data to inform decisions regarding the selection of salmonid strains that exhibit superior growth, survival, and product quality when raised in RAS.
Sub-Objective 2.2: All research activities were completed prior to FY2019. We continue to work with feed companies to assess diets with novel protein sources, and/or specific formulations designed to be RAS-friendly, i.e. to not significantly impact RAS water quality and unit process function and efficiencies. We have worked closely with ARS scientists to test novel diets in our replicated RAS, and moving forward we plan to conduct extra-ARS contract research with feed companies to evaluate novel diets in our new replicated (12) partial reuse systems. This line of research will be essential for assisting the growing land-based RAS industry through the development of feeds that do not degrade RAS water quality, provide excellent nutrition for superior fish growth performance and conversion, and are formulated with sustainable protein sources.
Accomplishments
1. Reduced bottlenecks in capital and operating costs for recirculating aquaculture systems. Land-based recirculating aquaculture systems (RAS) are becoming more common for production of salmon and trout, but high capital costs are a major obstacle for commercial implementation. Extramural ARS scientists in Shepherdstown, West Virginia, performed engineering and cost assessments to identify the major factors that can reduce high capital investments. These analyses indicated that larger RAS facilities, higher fish production, and efficiently designed tank space are significant for reducing costs of fish production. Scientists also determined how capital costs associated with tanks, pipes, and water pumps are affected by facility scale and layout. These findings provide the growing RAS industry with valuable information that reduces capital costs and water requirements, thereby improving energy efficiency and economic viability.
2. Determined effects of peracetic acid on rainbow trout and water quality in recirculating aquaculture systems. Peracetic acid (PAA) is used in industrial settings as a safe and low-cost disinfectant and powerful oxidant to improve water quality, but its potential benefit in recirculating aquaculture systems (RAS) has not been characterized. This led extramural ARS scientists in Shepherdstown, West Virginia, to evaluate the effects of PAA on water quality, growth performance, and off-flavor compounds in rainbow trout grown in RAS. Results of these investigations indicated that application of PAA in RAS did not change water quality, reduce off-flavor compounds in culture tank water, biofilms, and trout fillets, or negatively affect fish growth, survival, and feed conversion ratio. These findings inform the RAS industry of the impact of PAA relative to the traditional use of ozone as a disinfectant, provide a basis for continued research on PAA in RAS at different dosages and application regimens, and aid in the development of standard operating procedures to improve RAS water quality.
Review Publications
Davidson, J., Plautz, C., Grimm, C.C., Jorgensen, N.G., Podduturi, R., Raines, C., Snader, R., Good, C., Summerfelt, S. 2018. Evaluating the microbial effects of stocking freshwater snails (Physa gyrina) in water reuse systems culturing rainbow trout (Oncorhynchus mykiss). Journal of Applied Aquaculture. 31(2):97-120. https://doi.org/10.1080/10454438.2018.1541771.
Lepine, C.A., Christianson, L.E., Davidson, J.W., Summerfelt, S.T. 2018. Woodchip bioreactors as treatment for recirculating aquaculture systems’ wastewater: A cost assessment of nitrogen removal. Aquacultural Engineering. 83:85-92. doi:10.1016/j.aquaeng.2018.09.001.
Gorle, J., Terjesen, B., Summerfelt, S. 2019. Hydrodynamics of Atlantic salmon culture tank: Effect of inlet nozzle angle on the velocity field. Computers and Electronics in Agriculture. 158:79-91. https://doi.org/10.1016/j.compag.2019.01.046.
Davidson, J., Summerfelt, S., Straus, D.L., Schrader, K.K., Good, C. 2019. Evaluating the effects of prolonged peracetic acid dosing on water quality and rainbow trout Oncorhynchus mykiss performance in recirculation aquaculture systems. Aquacultural Engineering. 89:117-127. https://doi.org/10.1016/j.aquaeng.2018.12.009.
Mota, V., Nilsen, T., Gerwins, J., Gallo, M., Ytteborg, E., Baeverfjord, G., Kolarevic, J., Summerfelt, S., Terjesen, B. 2019. The effects of carbon dioxide on growth performance, welfare, and health of Atlantic salmon post-smolt (Salmo salar) in recirculating aquaculture systems. Aquaculture. 498:578-586. https://doi.org/10.1016/j.aquaculture.2018.08.075.
Gorle, J., Terjesen, B., Holan, A., Berge, A., Summerfelt, S. 2018. Qualifying the design of a floating closedcontainment fish farm using computational fluid dynamics. Biosystems Engineering. 175:63-81. https://doi.org/10.1016/j.biosystemseng.2018.08.012.
