Influence of pH and Temperature on Struvite Purity and Recovery from Anaerobic Digestate
J. Molina, Francisco
Camargo-Valero, Miller Alonso
The precipitation of struvite (MgNH4PO4.6H2O) from wastewater streams simultaneosuly recovers nitrogen (N) and phosphorus (P) for reuse as fertilisers. Struvite crystallisation is controlled by pH, saturation index, temperature and other ions in the solution (e.g., Ca2+, Mg2+ and CO32−). This work studies the effect of pH and temperature on phosphorus and nitrogen removal via struvite precipitation and the quality of the resulting precipitate product (i.e., crystal size, morphology and purity). Struvite was precipitated in batch reactors from the supernatant produced during anaerobic sludge dewatering at a wastewater treatment works, under controlled pH (8, 9 and 10) and temperature (25, 33 and 40 °C) conditions. The optimal P removal as struvite, reduction of the co-precipitation with Ca and the increase in particle size of the struvite precipitates were determined. The results showed that temperatures of 33 °C and 40 °C are not recommended for struvite precipitation—i.e., at 33 °C the purity is lower, and at 40 °C the ammonia losses are induced by volatilisation. At all pH-tests, the P removal efficiency was >93%, but the highest phosphate content and purity as struvite were obtained at a pH of 9.0. The optimum pH and temperature for the formation of large crystals (84 µm) and a high purity (>70%) of the struvite precipitates were 9 and 25 °C, respectively.
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Is part of
González-Morales, Carolina, Belén Fernández, Francisco J. Molina, Darío Naranjo-Fernández, Adriana Matamoros-Veloza, and Miller Alonso Camargo-Valero. 2021. "Influence Of Ph And Temperature On Struvite Purity And Recovery From Anaerobic Digestate". Sustainability 13 (19): 10730. doi:10.3390/su131910730.
Grant agreement number
INIA/Programa Estatal de I+D+I orientada a los retos de la sociedad/RTA2015-00093-00-00/ES/Integración de procesos para la oxidación sintrófica del acetato y autotrófica del amonio en el tratamiento anaeróbico de residuos orgánicos ricos en nitrógeno para su valorización energètica/PIONER
Gestió Integral de Residus Orgànics
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