Abstract
Red tide outbreaks kill great number of cultured fish resulting in the serious problem for fisheries. In this study, to clarify the ability of the foam-separation system for collection of red tide plankton, the optimum conditions of this system was investigated by batch system.
The results are as follows :
(1) It was clear that the foam-separating system was very effective for collecting plankton by combined use of a coagulant (poly ferric sulfate : PFS) and protein (casein). When added PFS and casein at dosage of 40mg-Fe·l-1 and 15mg·l-1, respectively, the recovery of Heterosigma akashiwo, Chattonella antiqua and Gymnodinum mikimotoi were 99%, and the ratio of volume of foam waste water to total amount of red tide seawater was about eight percent. The optimum dosages of PFS and casein for collecting diatom (Pheaodactylum tricornutum, Skeletonema costatum, Chaetoceros sociale) and H. akashiwo were less than that for above two red tide species.
(2) Approximately 100% of dosed PFS and casein were recovered from the treated seawater. Furthermore, about 99% of phosphate was removed from the red tide seawater by coagulation.
(3) AGP tests showed that the growth of red tide plankton (H. akashiwo, C. antiqua and G. mikimotoi) were strongly limited in the treated seawater.
