Fluoride Wastewater Treatment for Semiconductor Facilities

Calcium reacts with dissolved fluoride to form calcium fluoride, which is highly insoluble — that's what converts fluoride from a dissolved contaminant into a settleable/filterable solid the rest of the treatment train can physically remove.

Calcium fluoride precipitation efficiency is pH-dependent. A pH that drifts outside the controlled range reduces precipitation efficiency — the same reagent dose produces a worse result, which is exactly the kind of failure that looks like a chemistry problem but traces back to a control-system or dosing-pump specification gap.

The same specification gates as any dosing application — required dose range, backpressure, turndown, and whether flow-paced, feedback, or feedforward-plus-feedback-trim control fits the flow variability of the specific facility. ProMinent's Sigma series alone spans roughly 17–1,040 l/h across its Basic and Control tiers at pressures from 4–16 bar, which is enough range to cover most reagent and pH-trim dosing points on a fluoride train — but the actual model has to be selected against the real duty point, not picked from the middle of that range.

Combining them defeats the purpose of segregation — the calcium precipitation chemistry that removes fluoride works within a specific pH range, and a mixed acid/fluoride stream makes that pH control harder to hold, not easier. Segregating fluoride from general acid waste before treatment is the standard approach for exactly this reason.