Calcium phosphate precipitation in a fluidized bed in relation to process conditions: A black box approach

• Published in: Water research (Oxford) 1996, Vol.30 (7), p.1677-1685
• Main Authors: Seckler, M.M., Bruinsma, O.S.L., Van Rosmalen, G.M.
• Format: Article
• Language: English
• Subjects: Applied sciences; Bioreactors; Calcium; crystallization; eutrophication; Exact sciences and technology; fluidized bed; Fluidized beds; General purification processes; Ions; Magnesium; phosphate removal; Phosphates; Pollution; precipitation; Q1; Wastewater treatment; Wastewaters; Water treatment and pollution
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/0043-1354(96)00043-7

The precipitation features of calcium phosphate in a fluidized bed reactor in the concentration range between 5 and 100 mg P 1 −1 were studied, and the conditions for optimum phosphate removal efficiency were established. The supply of calcium ions should be such that a Ca/P molar ratio of 3 at the inlet of the reactor is achieved. If the water to be treated does not contain magnesium or carbonate ions, the supply of base should suffice to promote a conversion of 50–65% of the incoming phosphate to the solid phase. In the presence of carbonate and magnesium ions, the base supply should provide a conversion of 80–95%. Magnesium and carbonate ions did not have a detrimental effect on the phosphate removal efficiency for inlet concentrations of up to 4.8 × 10 −3 (Mg/P < 2 mol mol −1) and 1.8 × 10 −3 kmol m −3, respectively. The feasibility of a process based on the precipitation of magnesium phosphate instead of calcium phosphate was demonstrated for waters with a low calcium content (Ca/P < 0.8 mol mol −1). Finally a method is presented to select process conditions where co-precipitation of unwanted phases can be avoided.