Exploitation of acetic acid for calcite dissolution in small-capacity desalination plants

Post-treatment is essential to ensure hygienic desalinated water, and to prevent pipe corrosion. Calcite dissolution technologies are used to re-mineralise desalinated water via reverse osmosis, to enhance the calcium (i.e., hardness) and alkalinity concentrations therein. Sulphuric or carbonic acid is typically used for calcite dissolution but acetic acid can be exploited in small-capacity desalination plants. Of course, ultraviolet (UV) disinfection is an essential prerequisite because UV treatment does not contribute to the formation of disinfection byproducts (DBPs). Accordingly, we propose a specified acidification method that exploits acetic acid to optimise both the calcium and alkalinity concentrations via calcite dissolution. The process meets the regulatory standards for the calcium and alkalinity concentrations, and pH, of desalinated water. We found that acidification with strong acids (e.g., sulphuric or hydrochloric acid) yielded inappropriate calcium:alkalinity ratios. Calcite dissolution by acetic acid exhibited excellent dissolution kinetics, resembling those obtained using strong acids. We expect that our specified acidification method will facilitate calcite dissolution in small-capacity desalination plants.