Phosphorus recovery from anaerobic digester supernatants using a pilot-scale struvite crystallization process

• Published in: Journal of environmental engineering and science Vol. 6; no. 5; pp. 561 - 571
• Main Authors: Mavinic, D.S, Koch, F.A, Huang, H, Lo, K.V
• Format: Journal Article
• Language: English
• Published: Ottawa ICE Publishing 01.09.2007
• Subjects: anaerobic digester; Anaerobic digestion; Analytical chemistry; calcium carbonates; Canada, British Columbia, Vancouver; Chemical analysis; cristallisation; Crystallization; degré de sursaturation; digesteur anaérobie; dose de magnésium; déphosphatation; fluidized bed reactor; Magnesium; magnesium dosage; operational pH; Performance evaluation; pH de fonctionnement; Phosphate removal; Phosphorus; Phosphorus removal; Q1; Q3; réacteur à lit fluidisé; struvite; supernatant; supersaturation ratio; surnageant; trace metals; Wastewater treatment; Vancouver British Columbia Canada
• ISSN: 1496-256X; 1496-2551; 1496-256X
• DOI: 10.1139/S07-007

The performance of a pilot-scale, struvite crystallization process, for recovering phosphorus from various supernatants, was investigated. Using synthetic supernatant, as well as anaerobic digester supernatants from two full-scale wastewater treatment plants located in Vancouver, B.C., Canada, it was found that over 90% phosphate removal efficiency was achieved through controlling the supersaturation ratio, operational pH and magnesium dosage in the supernatant. With a high supersaturation ratio, or high operational pH, or high magnesium dosage, excellent phosphate removal was achieved. However, an operational pH greater than 8 was not necessary;; it was possible to control the process using a high magnesium dosage in place of a higher operating pH, but without a compromise in phosphate removal. Chemical analysis of the harvested crystals indicated very pure struvite (in excess of 91%), with only small amounts of residual calcium, carbonate, and trace metals. Most crystals exceeded 2 mm in mean diameter.