Recovery of plankton from red tide by HGMS

An experiment on the recovery of plankton from red tide by means of high gradient magnetic separation (HGMS) is reported using magnetic seeding method. The species of plankton, magnetic seeding material, and coagulant used in this experiment are Chattonella species, magnetite, and PAC (polyalumimum chloride), respectively. The dependence of the recovery on magnetite concentration, PAC concentration, residence time, pH, magnetic field intensity, and feed velocity is investigated. It is found that the optimum pH is about 9.3 and the optimum residence time is about 2 minutes. The recovery becomes as high as 100 % at residence time of 2 min, pH 9.3, PAC concentration of 100 mg/l, magnetite concentration of 100 mg/ℓ, magnetic field of 4×10⁵A/m=5 kOe, and feed velocity of 1.8 cm/sec.