Process for purifying glass industry waste waters

摘要

A process for purifying glass industry waste waters (effluents) is described which comprises adding lime to the waste water in a first separation phase up to a pH of 3-5, removing the resulting precipitate and further purifying the clear water in a second separation phase at a pH above 8.0. In the first separation phase, virtually all the amount of hydrofluoric acid present separates off as calcium fluoride and the majority of the sulphuric acid separates off as calcium sulphate. Since these precipitates contain most of the impurities present, but not the poisons, which cannot be stored in landfills, arsenic, antimony and lead, a precipitate is obtained in this manner which may be stored without risk in normal landfills. The poisons arsenic, antimony and lead do not arise until the second purification phase and pollute the relevant special waste landfills only to a slight extent because of the preliminary separation of the fluoride ions and sulphate ions.