Validity analysis of particles in the induced crystallization softening technology and optimization of the application mode

Abstract Induced crystallization softening technology has been widely used in applied drinking water treatment projects. The application mode needs to be optimized to achieve the complete utilization of induced crystallization particles. Therefore, a series of experiments were conducted to evaluate the change in induced crystallization particles, water hardness removal and effluent characteristics. Subsequently, the main determinants and the corresponding optimal operating mode were discussed. The results showed an increase in particle size, reaction time, and a decrease in solution pH reduced the water hardness removal efficiency of reactor. More likely, bigger crystallization particles slow down the water turbulence, cause uneven mixing of softening agents, decline the solution pH, and eventually softening reaction stop. Until Ref / Rep decreases to 1, the particles will completely lose the ability to remove hardness. The initial particle size and the dosage of softening agents as well as accelerating the up-flow velocity employed in the system were found to be key factor for the time particles take to reach a critical size and terminal velocity that stops the reaction. Therefore, filling the smaller particles and gradually increasing the up-flow velocity of the system could prolong the lifetime of the particles in practical applications, improving the utilization efficiency of the unit volume. Furthermore, it optimizes the sand discharge cycle and produces safer waste residues.