Removal of phosphorus and nitrogen is required to prevent eutrophication problems in lakes and enclosed coastal seas. And recovery of phosphorus from wastewater has been attracting attention because of lack in phosphorus resources in the near future. In this study, reaction kinetics and design parameters of struvite production are experimentally investigated by using basic reaction type and a draft-tube type reactors. Struvite production rate, which is a very important parameter in reactor design and efficiency estimation, is formulated in an equation consisting of a rate constant (k2), and magnesium, phosphate and ammonium concentrations. The value of k2 is shown to be increased with struvite concentration and mixing intensity in the reactor. The developed equation is applied to the results obtained from the draft-tube type reactor experiments and verified for its applicability. High struvite concentration of 10-25% is maintained in the draft-tube reactor experiments. 92% removal and recovery efficiency with effluent phosphorus concentration of 17 mg/L is achieved under the conditions of 4 minutes reaction time, pH of 8.5 and Mg/P molar ratio of 1.1.

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Reaction of the alkyl ketene dimer and hydroxyl radicals in the presence of catalysts was studied.Tetradecyl ketene dimer was chosen as the alkyl ketene dimer.p-Toluen sulfonic acid, KOH and KHCO3 were used as the catalysts. Primary, sec-, tert-BuOH, ethylene glycol, phenol and H2Owere used as the hydroxyl radicals.As a result, the reaction products of alkyl ketene dimer with hydroxyl radicals, except H2O, were esters of 2-alkyl-3-keto acid.Basic catalysts gave larger reaction velocity than acidic catalysts to hydroxyl radicals with the exception of phenol. Sec-, tert-BuOH and H2O which were difficult to react by the acidic catalysts, have readily reacted comparatively by using basic catalysts and the ketone was obtained with H2O. The ester of keto acid was obtained by using KHCO3 and by a small quantity of KOH. However, ketone was obtained with KOH by using more than equivalent of the alkyl ketene dimer.

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