Submitted to: International Conference on Recirculating Aquaculture
Publication Type: Proceedings
Publication Acceptance Date: 6/1/2010
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: In recirculating aquaculture systems (RAS), the water which is treated and reused must be of such quality to maintain the culture organism in a healthy and fast growing condition, especially as such systems are intensified. Managing particulate matter and different chemical compounds is a key factor for the successful operation of a RAS. The presence and accumulation of particulate wastes can cause a decline in water quality that can result in an unhealthy and poor growth condition for the organism being cultivated. There are several types of commercial available particle removal or separators devices for integration into an intensive RAS. Solids removal devices in an intensive RAS can be divided into a mechanical or gravitational method. The use of rotating microscreens is a popular method for the mechanical particle removal, however, the removal of fine solids smaller than 50 microns from the water is difficult. As a result, particles of this size tend to build up in a recirculating system and need to be removed. Foam fractionation is a mechanical water treatment technology that can be easily employed and integrated into an RAS to directly remove these dissolved and fine, suspended solids that are less than 50 microns in size. This study investigated the efficiency of the foam fractionation system for removing and reducing particulate materials from the low salinity water of a red drum RAS for different modes of operation. The RAS consisted of 4 rearing tanks (3.05 m in diameter and 1.0 m in depth), a foam fractionator, a moving bed biofilter unit, a rotating microscreen drum filter with a 40 micron screen, and a UV unit. System tank culture density was approximately 60 kg/m3, the daily system feed rate was maintained at 18 kg/day, and system salinity was maintained in a range between 11 and 13 ppt. The foam fractionator was timer controlled to operate after daily feedings ceased and before morning feedings started (2200-1000) for three periods of three hours each. The flow through the unit ranged between 225 to 305 Lpm providing a hydraulic retention time between three and four minutes. Timer operations were set to provide three system volume turnovers per evening of operation. The efficiency of the foam fractionator was analyzed for different operating heights, different methods of bubble injection – venture and submersed pump, and the use of ozone. Unit efficiency was determined by the amount of dissolved and suspended solids removed, volume of the foam rinsate, overall solids removal efficiency, and removal efficiency of particles less the 50 microns from the water reuse stream. Results indicated greater particle removal with the use of ozone and at a higher operating water height.