AWWA JAW62320

Water softening can help alleviate problems caused by hard water, such as hindering of laundering processes and scale buildup in hot water pipes and heaters. This article summarizes the fundamental aspects of softening and explains the effect of improving the process with the use of seed crystals. Heterogenous nucleation, which refers to precipitation on the surface of nucleating agents such as seed crystals, lowers the free energy of crystallization in precipitative water softening processes. To determine the importance of the amount of surface area provided by the nucleating agent, the authors added different- sized calcium carbonate seed crystals to various hard waters during precipitative softening with caustic soda. As these results demonstrated, the surface area of the seed crystals, rather than the total mass, proved the key factor in the optimization of the softening process. Includes 35 references, tables, figures.