Location: Cool and Cold Water Aquaculture ResearchTitle: Low head oxygenator performance characterization for marine recirculating aquaculture systems Author
|Vinci, Brian - Freshwater Institute|
|Davidson, John - Freshwater Institute|
|Naveh, Eyal - Grow Fish Anywhere Advanced Systems, Llc|
|Engler, Or - Grow Fish Anywhere Advanced Systems, Llc|
Submitted to: Aquacultural Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2016
Publication Date: 10/12/2016
Citation: Vinci, B., Davidson, J., Naveh, E., Engler, O. 2016. Low head oxygenator performance characterization for marine recirculating aquaculture systems. Aquacultural Engineering. 22:22-28.
Interpretive Summary: The low-head oxygenator (LHO) is an efficient oxygenation technology commonly used for intensive fish production in freshwater recirculating aquaculture systems (RAS). The LHO technology effectively supersaturates the culture water with oxygen, thereby maximizing fish biomass production in a given water volume. Reliable data that characterizes LHO oxygenation efficiency within marine recirculating aquaculture systems is limited. The effect of temperature (20 and 25 ºC), salinity (10, 15, and 20 ppt), and dissolved oxygen levels on oxygen transfer efficiency of LHOs was evaluated for a planned marine recirculating aquaculture system. LHO oxygen transfer efficiency in marine RAS was found to be affected by salinity and required dissolved oxygen at the LHO outlet. Improved performance for similarly-designed LHOs in intensive marine RAS can be achieved by designing LHOs with lower hydraulic loading, taller water fall height, and increased submergence. These engineering details are critical in optimizing LHO design for marine RAS applications. The knowledge gleaned from this research can be used in predictive modeling for marine fish production in RAS to determine important metrics such as maximum fish biomass and feed loading, and ideal LHO operation.
Technical Abstract: This study evaluated the effect of temperature (20 and 25 ºC), salinity (10, 15, and 20 ppt), and dissolved oxygen levels within low head oxygenator (LHO) outlet water on oxygen transfer efficiency (OTE) of LHOs for a planned marine recirculating aquaculture system (RAS). Test results indicated that OTE was generally greater at salinities of 10 -15 ppt compared to OTE measured with freshwater and at 20 ppt salinity. Oxygen transfer efficiency in freshwater with LHO outlet oxygen saturation of 230 % was only 58 % compared to OTE in 10 ppt and 15 ppt salinity with an LHO outlet oxygen saturation of 230 % of 79 % and 72 %, respectively. As expected, OTE declined as target dissolved oxygen levels in LHO outlet water increased from 150 to 230 % saturation. Oxygen transfer efficiency at 15 ppt salinity and 150 % dissolved oxygen saturation at the LHO outlet was 97 %, while OTE dropped to 72 % at 230 % oxygen saturation. Increased OTE at higher salinities of 10 -15 ppt was attributed to increased ionic strength of the water under saline conditions resulting in formation of smaller diameter bubbles, as opposed to larger bubbles formed in freshwater. However, at 20 ppt this effect may have caused the formation of small diameter bubbles with such a slow rise velocity that they were overcome by the water velocity leaving the bottom of the LHO and were carried out of the LHO, thereby reducing OTE. Improvements in performance for similarly-designed LHOs in intensive marine RAS can be realized by designing LHOs for lower hydraulic loading, taller fall height, and increased submergence.