• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.5
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• pp.448-454
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• 2000

This study was to examine the physicochemical characteristics of coagulation reaction between ignited oyster shell powder (IOSP) and red tide organisms (RTO), and its feasibility, in developing a technology for the removal of RTO bloom in coastal sea,IOSP was made from oyster shell and its physicochemical characteristics were examined for particle size distribution, surface characteristic by scanning electron microscope, zeta potential, and alkalinity and pH variations in sea water. Two kinds of RTO that were used in this study, Cylindrotheca closterium and Skeletonema costatum, were sampled in Masan bay and were cultured in laboratory. Coagulation experiments were conducted using various c(Incentrations of IOSP, RTO, and a jar tester. The supernatant and RTO culture solution were analyzed for pH, alkalinity, RTO cell number, IOSP showed positive zeta potentials of $11.1{\~}50.1\;mV\;at\;pH\;6.2{\~}12.7$, A positive zeta potential of IOSP slowly decreased with decreasing pNa 4,0 to 2,0. When pNa reached zero, the zeta potential approached zero, When a pMg value was decreased, the positive zeta potential of IOSP increased until pMg 3.0 and decreased below pMg 3.0. IOSP showed 4.8 mV of positive zeta potential while RTO showed -9.2 mV of negative zeta potential in sea water. A positive-negative EDL (electrical double-layer) interaction occurred between $Mg(OH)_2$ adsorption layer of IOSP and RTO in sea water so that EDL attractive force always worked between them. Hence, their coagulation reaction occurred at primary minimum on which an extreme attractive force acted because of charge neutralization by $Mg(OH)_2$ adsorption layer of IOSP. As a result, the coagulation reaction was rapidly processed and was irreversible according to DLVO (Deriaguin-Landau-Verwey-Overbeek) theory. Removal rates of RTO were exponentially increased with increasing both IOSP concentration and G-value. The removal rates were steeply increased until 50 mg/l of IOSP and reached $100{\%}\;at\;400\;mg/l$ of IOSP. Removal rates of RTO were $70.5,\;70.5,\;81.7,\;85.3{\%}$ for G-values of $1,\;6,\;29,\;139\;sec^(-1)$at IOSP 100 mg/l, respectively. This indicated that mixing (i.e., collision among particles) was very important for a coagulation reaction.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.36 no.6
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• pp.716-722
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• 2003

This study determined the optimum dosage for coagulation reactions of red tide organisms (RTO) using a combination of ignited oyster shell powder (10sp) and loess and examined the electrokinetic and rheological characteristics of their flocs. Two kinds of RTO, Cylindrotheca closterium and Skeletonema costatum, were sampled in Masan Bay and cultured in the laboratory. Coagulation experiments were conducted using various concentrations of IOSP, loess, IOSP+1oess, RTO, and a jar tester RTO cell numbers were counted for both the supernatant and RTO culture solution. The removal rates increased rapidly with increasing IOSP concentrations up to 50 mg/L and loess concentrations up to 800 mg/L. A removal rate of $100\%$ was reached at 400 mg/L of IOSP and 6,400 mg/L of loess. The highest increment $(16.7\%)$ of the rates of coagulation reaction occurred using both IOSP and loess (50+200 mg/L) in comparison with IOSP alone. The rate of coagulation reaction using both IOSP and loess (50+200 mg/L), $90.6\%,$ was similar to employing either IOSP of 150 mg/L or loess of 3,200 mg/L. All of the coagulation liquids for RTO, IOSP (200 mg/L), loess (200 ma/L), and IOSP+1oess (200+200 mg/L) revealed non-Newtonian fluid properties and therefore their shear rate vs. shear stress curves were non-linear. The coagulation liquids revealed elastic body properties at a lower shear rate increasing in the following order: RTO, IOSP (200 mg/L), loess (200 mg/L), and IOSP+1oess (200+200 mg/L. IOSP+1oess (200+200 mg/L) especially demonstrated plastic flow properties at a lower shear rate.