Phosphate removal in anaerobic liquors by struvite crystallization without addition of chemicals: Preliminary results

• Published in: Water research (Oxford) 1997-11, Vol.31 (11), p.2925-2929
• Main Authors: Battistoni, P., Fava, G., Pavan, P., Musacco, A., Cecchi, F.
• Format: Article
• Language: English
• Subjects: Anaerobic digestion; Applied sciences; Biological and medical sciences; Biological treatment of sewage sludges and wastes; Biotechnology; Chemicals removal (water treatment); Crystallization; Environment and pollution; Exact sciences and technology; Fluidized beds; fluidized-bed reactor; Fundamental and applied biological sciences. Psychology; Industrial applications and implications. Economical aspects; Ions; magnesium ammonia phosphate; Other industrial wastes. Sewage sludge; Phosphates; phosphorus removal; Pollution; Sewage aeration; Sewage sludge; struvite; Supersaturation; Wastes
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/S0043-1354(97)00137-1

The feasibility of phosphate removal from the supernatant of anaerobically digested sludge by struvite (MAP, MgNH 4PO 4) crystallization in a fluidized-bed reactor (FBR) was studied. Quartz sand was used as seed material. Three successive steps were investigated to highlight the process: 1, natural aging of the supernatant, with phosphate concentrations in the range 18–164 mg/l, which gave good crystallization of struvite within 3 days; 2, the inhibiting effect of Mg and bicarbonate ions on hydroxyapatite (HAP, Ca 5OH(PO 4) 3) formation, which leads to struvite formation under supersaturation conditions; and 3, phosphate removal via the process of complete crystallization on the seed material, and which is obtained by means of external continuous aeration. All runs were performed without the addition of chemicals.