Optimization of chemical usage through constant monitoring of calcium ions in the sedimentation tank

Hydrofluoric acid in wastewater at semiconductor plants is removed by injecting calcium-based chemicals, coagulating it as calcium fluoride, and removing it via sedimentation. When doing so, to adequately lower the fluorine concentration in response to changes in water quality, it was common to inject an excess amount of calcium-based chemicals. However, excess injection not only raises chemical costs, it also causes the problem of an increase in facility maintenance from increased sludge and scale.

・Cannot continuously measure excess calcium ion concentration post-treatment.

Previously there were no calcium ion meters capable of continuous measurement, so there was no method for continuously monitoring whether the chemicals injected in line with the fluoride concentration were of the appropriate amount. HORIBA’s Calcium Ion Meter provides an indicator to guide optimal chemical injection by continuously monitoring calcium ion concentration in the sedimentation tank.