FISH FARMING TECHNOLOGY downwards to 40cm below the surface of the One of the key process technologies required water. for intensive fish farming is dissolving oxygen These buoyant bubbles flow upwards, counter to gas into the farm water. There are many the downward water flow in such a way that the technologies available to accomplish this, downward velocity is not strong enough to carry ranging from simple low head oxygenators the bubbles out of the chamber, hence the only (LHO) to very elaborate, multi-stage way the oxygen gas can escape the Oxyflow® processes operating at elevated pressures and controlled by computers. unit is to become dissolved in the water. Bubbles What the commercial fish farmer really wants that break the water surface inside the unit Henning Gatz and needs is a simple, reliable process for are again subjected to the turbulence of the President of Aquacare Environment Inc. dissolving oxygen gas into the water that does downward jets until they become dissolved. not cost more than necessary and can be maintained by farm Thus, the goal of reliable, cost effective transfer of gaseous oxygen personnel without a huge time requirement. Above all it needs to be into dissolved oxygen is accomplished. While the oxygen use reliable, even during disruptive events like power failures. efficiency of the Speece Cone may be marginally higher than In 2010, JLH Consulting and Aquacare began an initiative to lower the Oxyflow®, the 5 x energy cost of the Speece Cone more than the cost of land-based intensive fish farming operations. This outweighs such benefits. initiative focused on two of the largest cost factors: pumping head and An example would be dissolving 10kg O2/h at 28°C into fish oxygenation. The pumping head has now been reduced by several farm water. The Oxyflow® requires 3.9 kW while the Speece Cone meters by lowering the biofilter and CO2 strippers to a level where requires 21.4 kW, a savings of 82 percent for the Oxyflow®. This gravity can supply them, and only pumping clean filtered water back translates into over US $18,000 savings per year with electricity to the fish tanks with high flow, low head pumps. This reduction in at $0.12/kWh. The savings are even better at cooler water pumping head led to another challenge: oxygenation with lower head. temperatures. These savings are due to the Oxyflow® operating at In 2012, we had the good fortune to meet the people at France 0.3 bar versus three bar for the typical Speece Cone. Oxygenation (FOX) who have developed and market a simple, The Oxyflow® and its related devices have been in use on fish reliable and efficient oxygen saturator under the name of Oxyflow®. farms in Europe since 1994. There is currently an installed base of over 200 units in Europe, 61 units in the US and Canada, and 33 in Upon closer examination, this unit process technology was exactly Australia. The Oxyflow® has a very reliable design, with no moving what we were seeking to lower the cost of dissolving large amounts of oxygen into the fish farm water, reliably and efficiently. parts or restrictive passages. FOX was established as a specialist oxygenation technology The traditional Speece Cone is somewhat similar but only with one company in 2005, after founder Bohumil Sevic developed the large jet at high pressure instead of multiple low-pressure jets that technology in 1977 as a research engineer for Air Liquide in create more oxygen/water contact area at much lower pressure. The France. He was able to retain the IP after leaving Air Liquide. Since LHO is also similar but loses head as water flows through it and is then Mr Sevic has continued to refine and evolve the technology to less efficient at dissolving oxygen. where it is today. Furthermore, the Oxyflow facilitates the oxygenation of all the Essentially, the Oxyflow® is an LHO that operates in a sealed water supplied to the fish tank, not just a side-stream loop, for more consistent oxygen levels throughout the tank. This has important vessel thus not breaking head pressure. Process water enters the benefits for the fish in the tank, with better mixing and more even top of the unit under mild pressure of about 0.3 bar. The water oxygen distribution inside the tank. The Oxyflow® can be combined next passes through a horizontal drilled plate with specially shaped orifice holes (number and size determined by flow rate required) with a constant pressure pump to maintain proper flow through the which jets the water downward though an oxygen atmosphere process unit under varying conditions. A barge mounted option is approximately 20cm deep. available for oxygenation of sea cage sites. When the jets strike the water surface below, they cause a high OxyFlow® is distributed in North America and Australia by turbulence and create a bubble cloud of pure oxygen that extends Aquacare Environment Inc.
FISH FARMING TECHNOLOGY KRILL: The Antarctic Endurance: A pioneering feat of marine technology - page 36
SPECIES EXPERT TOPIC: Atlantic Halibut - page 46
SHRIMP: The shrimp feed sustainability conundrum - page 24
Aquaculture round-up
MONACO BLUE INITIATIVE: Ocean MPAs to become more inclusive for all stakeholders - page 26