High-rate calcium removal using the Hyperkinetic Vortex Crystallization (HVC) process for reuse of electronics wastewater

Abstract

The Hyperkinetic Vortex Crystallization (HVC) process using hydrodynamic cavitation technology was investigated to remove high calcium levels from the effluent of the fluoride removal process used in a semiconductor manufacturing company. Due to low alkalinity in the effluent of this wastewater, addition of sodium carbonate was necessary. The relatively stable effluent calcium concentration of 8.0–52.8 mg/L was achieved although the influent calcium concentration severely fluctuated in the range of 173–371 mg/L. A calcium removal efficiency of 84.5–97.0% was determined with the HVC process. To confirm the cavitation effect, the calcium removal process was operated with and without the use of the VRTX cavitation system. The calcium removal efficiency increased from 63.5% to 91.7% when the VRTX unit was operating. The change of the calcite shape from plate to a spherical form by VRTX application was also observed. This can 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 (limit) formation of calcite scale in the inner wall of pipes and reactors.