Abstract
Artificial seed crystal of calcium silicate hydrate (5CaO·6SiO2·5H2O: tobermorite crystals) was developed for crystallization of calcium phosphate. The crystallization process using the seed material was examined to confirm the stable removal of phosphorus from secondary effluent of municipal wastewater. The effects of the operating parameters on the crystallization process were analyzed with long term experimental data. Water temperature, pH and concentration of calcium ion were selected as the parameters in order to control stable and high removal efficiency of phosphorus. The effect of the operating parameters on the efficiency of crystallization process was shown by the experimental results. It is shown that the crystallization reaction can be expressed as first-order equation. A practical operation of the crystallization process using calcium hydroxide was demonstrated to obtain the long-term performance under the appropriate condition of pH value. It was experimentally clarified that the rate constant of the crystallization reaction decreased in proportion to the decrease in the calcium ion concentrations.
