Treatment of phosphate-containing wastewater with fluorosilicate and phosphate recovery

A system for treating phosphate-containing wastewater from a phosphogypsum pond, the system comprising:

• an input connected to draw in phosphate-containing wastewater from a phosphogypsum pond;
• a fluorosilicate precipitation stage comprising one or more first vessels connected to receive the phosphate-containing wastewater from the input and a first reagent injection mechanism arranged to deliver a first reagent comprising a first cation to the wastewater in one or more of the one or more first vessels to precipitate fluorosilicate from the wastewater;
• a fluoride removal stage comprising one or more second vessels connected to receive liquid effluent from the fluorosilicate precipitation stage and a second reagent injection mechanism arranged to deliver a second reagent comprising a second cation and a base to the wastewater in one or more of the one or more second vessels to precipitate fluoride from the wastewater;
• a settling tank connected to receive liquid effluent from the fluoride removal stage;
• and
• a recirculating crystallizer connected to receive liquid effluent from the settling tank, the crystallizer configured to precipitate a phosphate-containing compound from the wastewater and comprising a mechanism for harvesting particles of the phosphate-containing compound.