**1. Introduction**

Calcium carbonate CaCO3 is a commercial material and a major constituent in many natural systems. CaCO3 is widespread in the natural environment such as eggshells, corals, and sedimentary rocks [1–3]. CaCO3 is applied as filler and pigment in the production of paper, rubber, plastic, paint, textiles, and pharmaceuticals [4, 5]. More interesting, CaCO3 is used in ionic cements which are widely used in bone and dental replacement biomaterials. Original compositions of bioresorbable and biocompatible cements including a significant proportion of synthetic CaCO3 have been developed to meet a need for biomedical cements with

increased resorption properties. Bone substitutes based on chemically treated natural CaCO3 are biocompatible and bioactive. They are used in the form of powder and porous ceramics [6–11]. Because of the higher solubility of calcium carbonates compared to calcium phosphates, the introduction of a significant amount of a metastable variety of CaCO3 (vaterite or aragonite) should give mineral cements a higher rate of resorption and thus promote faster bone reconstruction [11, 12].

On the other hand, CaCO3 has a significant impact on energy production and water treatment. The insufficiency of the freshwater resources and the requirements of drinking water will be increasingly manifest in the years to come. It is very probable that the problem of water, just like that of the energy resources, will be regarded as one of the determining factors of the stability of a country. The surest and economic means to supply the drinking water populations require the desalination of brackish, saline or sea waters by using different processes of desalination (reverse osmosis, electrodialysis, distillation, etc). However, these processes are generally of large-scale consumers of energy and confronted with various problems, such as corrosion and scale formation (**Figure 1**) which cause enormous energy losses. In most cases, scales are made of the sparingly soluble salt CaCO3 [13–19]. Because of its poor thermal conductivity and its good adherence to the walls, CaCO3 decreases the heat transfer rate, reduces the water flow rate, and even shortens equipment life by corrosion [20, 21]. The crystallization of CaCO3 depends on several operating parameters such as the mineralogical water composition, the supersaturation of the treated water, the pH, and the temperature.

In the present overview chapter, I was interested in the scale problem through CaCO3 precipitation encountered during drinking water and wastewater treatment plants. The effect of the operating parameters such as temperature, pH, supersaturation, and foreign ions on the CaCO3 crystal growth, microstructure and polymorphism was exposed. Knowledge about these operating parameters for CaCO3 crystallization as well as the effects of foreign ions, especially magnesium, sulphate, and iron ions, is very important in the elucidation of the CaCO3 polymorphs growth during water treatment. The presence of mineral ions can have a major influence on the crystal growth and microstructure of CaCO3 since they are present with significant concentrations in natural waters. The economic impact is of the utmost importance. Indeed, the control of the operating parameters makes it possible to inhibit or reduce the scale formation during the treatment of drinking water and wastewater in different industrial processes such as desalination units, water pumps

**Figure 1.** *Scaling through CaCO3 precipitation in drinking water pipes.*

*Effect of Operating Parameters and Foreign Ions on the Crystal Growth of Calcium Carbonate… DOI: http://dx.doi.org/10.5772/intechopen.94121*

and heat exchangers. This positively affects processing costs, increases the life of the equipment, and enhances the product water recovery.
