WWW.WAS.ORG • WORLD AQUACULTURE • MARCH 2014 21 (CONTINUED ON PAGE 22) filters followed by submerged fixed-bed, moving-bed and trickling biofilters, with an apparent capacity to treat waste from 3000 kg feed daily. Following these processes, water is pumped to a head tank where it gravity flows through oxygenation columns before returning to each culture tank. The single center-drain culture tanks are made from pre-cast panels with a high-quality, smooth concrete finish. Each tank is flushed approximately every 45 minutes with recirculating water. They stock post-smolts into the grow-out system, first into 8.5 m diameter tanks, then 10.2 m diameter tanks, and finally 14.2 m diameter grow-out tanks for a total of about 10 months until harvest. Several purge tanks are plumbed to operate either on flow-through or water from the grow-out recirculation system. Densities are allowed to reach 85-100 kg/m3, depending upon life stage in the growout facility. Fish are removed from these large and deep (6 m) culture tanks using a purse seine to pull fish to the pump intake followed by portable hoses and a large vacuum pump. Fish are pumped to a dewatering box (water flows back to the RAS) and onto a hand-sorting table before they enter the next tank. Harvested fish will be hauled live to the processor when harvest begins at the end of 2013 or early 2014. The total grow-out period is expected to be less than 24 months (from egg hatch) to harvest a 4 to 5 kg salmon. German Merino (Universidad Catolica del Norte, Chile) presented trends for Atlantic salmon production in land-based systems in Chile. He provided a detailed review of the rapid expansion in the use of RAS to produce Atlantic salmon smolts and even broodfish. Continued refinement in technologies has improved system performance and reduced overall electrical operating costs in later-generation RAS. These first projects, particularly the ‘Namgis First Nation’s salmon farm and the Taste of BC steelhead farm, will begin to identify the fish production costs, market potential, and overall economics of salmon produced to food-size in land-based closed-containment systems. Quantifying and communicating the economic viability of raising salmon in closed-containment facilities is critical to the success of this industry. For these reasons, these two farms aim to be completely transparent and all the information collected during the first three production cycles will be available to all interested parties. Lessons Learned While Engineering and Building Commercial RAS Ivar Warrer-Hansen (Inter Aqua Advance A/S, Denmark) opened the session with an interesting case-study on challenges in construction and operation at extremely remote RAS locations, such as Finmark, Norway. Gary Robinson (GRV Inc., Canada) discussed a comprehensive retrospective assessment of construction costs for the first 400 mt/y Atlantic salmon grow-out module at the ‘Namgis First Nations. Mr. Robinson identified several areas where savings could be made in concrete construction and where economies-of-scale were realized in unit processes, such as tanks, pumps, and filters. He also itemized areas where improvements would realize savings when the ‘Namgis build their second of five planned grow-out modules (total 2500 mt commercial scale). Creating Value from the Waste Stream Summit attendees had great interest in reuse benefits associated with waste streams from land-based closed-containment fish farms. Norman McCowan (Bell Aquaculture, USA) discussed his success in this arena due to Bell Aquaculture’s innovative and revenue-creating conversion of fish processing offal and thickened fish manure (Fig. 4) into marketable organic fertilizers and soil amendments. Aquaponics was another hot topic with Thomas Losordo and Huy Tran (Pentair Aquatics, USA) providing an interesting case study about Urban Organics, an aquaponics facility in Minneapolis, Minnesota. RAS Design Innovations and Opportunities in Land-Based Closed-Containment Systems Marius Haegh (Krugerkaldnes/Veolia, Norway), Thomas Losordo (Pentair Aquatics, USA), and Bjarne Hald Olsen setLEFT, FIGURE 3. Submerged filters (left), moving bed biofilters (middle) and trickling filters (right) in the central water treatment area at Langsand Laks, Denmark (Photo: Steven Summerfelt/The Conservation Fund). RIGHT, FIGURE 4. Bell Aquaculture LLC (Albany, Indiana, USA) uses four gravity thickening settling units (each 4 m dia x 5.5 m deep) to capture and dewater biosolids in their RAS facility discharge before this flow is further treated in a created wetland (Photo copyright © 2014 Bell Aquaculture LLC™ — All Rights Reserved).
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