Pretreatment of Electronics Wastewater for Reuse: Removal of Calcium Using Controlled Hydrodynamic Cavitation

Controlled Hydrodynamic Cavitation (CHC) was investigated to remove high calcium levels from the effluent of the fluoride removal process used at a semiconductor manufacturing company. To confirm the cavitation effect, the current calcium removal process was operated with and without the use of the CHC system. The calcium removal efficiency increased from 63.5% to 91.7% when the CHC unit was operating. The change of the calcite shape from plate to a spherical form by application of CHC was also observed. The spherical shape can effectively enhance calcium removal because of the larger specific surface area for adsorption of newly produced colloidal calcites. The conversion of the calcite shape to spherical would also prevent or limit formation of calcite scale on the inner wall of pipes and reactors within the treatment system.