Vivianite for Phosphorus Recovery from Digester Supernatant in Wastewater Treatment Plants

Phosphorus (P) recovery by crystallization of vivianite in digester supernatant (DS) was investigated. A high recovery yield (> 90 %) was obtained with vivianite even for DS with low P concentration (74 mg L-1), as opposed to the formation of struvite and hydroxyapatite where the yield was lower than 50-60 %. Various strategies were tested to produce vivianite with large sizes and narrow size distribution, such as a controlled reagent dosing profile, self-seeded crystallization, and multistage cascade-seeded crystallization. The obtained results demonstrated that the main challenge in the development of vivianite P recovery is to promote crystal growth and to suppress secondary nucleation of vivianite during the crystallization process.

Automated summary

This study investigated the recovery of phosphorus through crystallization of vivianite in digester supernatant. It was found that vivianite achieved a high recovery yield even in digester supernatant with low phosphorus concentration. Various strategies were tested to obtain vivianite crystals with large sizes and narrow size distribution.