Effect of C/Ca Ratio on Crystallization of CaCO3 during Calcium Hardness Removal in Drinking Water
China Water & Wastewater[ISSN:1000-4062/CN:12-1073/TU]
volume:
第36卷
Number:
7 7
Page:
37-41
Column:
Date of publication:
2020-04-01
- Keywords:
- calcium hardness; crystallization of CaCO3; C/Ca ratio; supersaturation; pH
- Abstract:
- The removal efficiency of calcium hardness in drinking water is mainly affected by CaCO3 crystallization process. The removal of calcium hardness in drinking water was simulated by changing the C/Ca ratio. Variations in pH value and Ca2+ concentration of the solution system and turbidity of the supernatant, and particle size distribution, polymorph and crystal shape of the crystallized products were investigated under different C/Ca ratios, so as to clarify the crystallization behavior of CaCO3 during the removal of calcium hardness. Calcite was the only crystallized product in the present experimental conditions. The addition of CO2-3 to the solution first protonized and increased the pH value of the system, and then it crystallized with Ca2+ and reduced the pH value of the system. The increase of C/Ca ratio increased the pH value and was conducive to the removal of Ca2+. However, it also increased the particle number and density of the crystallized products and reduced the particle size of the crystallized products, resulting in the increase of the turbidity of the supernatant. Therefore, factors such as residual Ca2+ concentration, pH value and turbidity of the supernatant, and the dosage of coagulant should be comprehensively considered to determine the optimal C/Ca ratio during calcium hardness removal in drinking water.
Last Update:
2020-04-01