silicofluoride complexes = hydrofluorosilicic acid & sodium silicofluoride.
In other words: (sodium) silicofluoride is not (sodium) Fluoride.
silicofluoride (= silicon dioxide and sodium fluoride) is added to watersupplies.
hydrofluorosilicic is a wasteproduct from the fertilizer (phosphate) industry, and is added to watersupplies.
"However, the US phosphate industry has thus far been unable to take advantage of this market. The principal reason for this failure stems from the fact that fluoride captured in the scrubbers is combined with silica. The resulting silicofluoride complex has, in turn, proved difficult for the industry to separate and purify in an economically-viable process."