Water Quality Characteristics
Industrial fluoride-containing wastewater mainly comes from the discharged water from the cleaning process and polishing process before, during and after the glass etching and thinning. During the etching process, after filter-element circulating filtration, the concentrated hydrofluoric acid (HF) is discharged, collected, outsourced and treated on a regular basis, so the concentrated hydrofluoric acid won’t enter the wastewater treatment system. The main pollution agents in the wastewater are acidity, high-concentration fluorin-ion, high-concentration ammonia nitrogen and suspended substances, which have the characteristics of bad biochemical quality, high corrosion and big hazard, and if it is directly discharged, it will cause severe impact on the natural environment and people’s live.

Thought for Treatment
An overall process of pretreatment + ammonia nitrogen blow-off + three-stage coagulating sedimentation + sand filtration + fluoride-removing filter are adopted. The wastewater is collected in the collecting pipe, then it flows into the regulation tank under gravity, and then by evenly mixing various components of the water through stirring by the compressed air, it enters the ammonia nitrogen blow-off tower, where the blow-off method is used to remove ammonia nitrogen; then it enters the three-stage coagulating sedimentation tank, where the online pH device is used to regulate the pH value and dosage to covert as much fluorinion to CaF as possible to precipitate; then it enters the three-stage sedimentation tank for sludge-water separation, the supernatant flows back to the middle pond, certain suspended substances will be filtered by the sand filter, and the it flows back to the fluoride-removing filter to further remove the fluoride; the effluent can enter the biochemical system of the wastewater treatment station for continual treatment or discharged directly. The supernatant from the sludge concentration tank and the filtrate from the sludge dehydration machine flow back to the regulation tank through the collecting pipe, and the sludge will be delivered out after pressure filtration.