Struvite Phosphorus Recovery from Aerobically Digested Municipal Wastewater

John F. Hallas, Cheryl L. Mackowiak, Ann C. Wilkie and Willie G. Harris
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John F. Hallas: Talquin Electric Cooperative Inc., Quincy, FL 32351, USA
Cheryl L. Mackowiak: North Florida Research and Education Center, University of Florida-IFAS, Quincy, FL 32351 USA
Ann C. Wilkie: Soil and Water Sciences Department, University of Florida-IFAS, Gainesville, FL 32611 USA
Willie G. Harris: Soil and Water Sciences Department, University of Florida-IFAS, Gainesville, FL 32611 USA

Sustainability, 2019, vol. 11, issue 2, 1-12

Abstract: Small, municipal wastewater treatment plants (WWTPs) that use aerobic digestion treat approximately 40% of the discharged wastewater in the USA, and yet they are an overlooked source of recoverable P. There are no known reports of small, aerobic WWTPs recovering P through struvite (MgNH 4 PO 4 ·6H 2 O) precipitation for repurposing as a mineral fertilizer, even though some large WWTPs with anaerobic digestion are. Four small WWTPs in north Florida, USA, with treatment capacities from 371 to 2650 m 3 wastewater d −1 and incoming P loads from 2 to 14 kg d −1 were investigated for their potential to produce struvite from digester filtrates. A chemical equilibrium model was used to predict the feasibility of struvite production and the results compared with actual WWTP filtrate measurements. Filtrates from aerobic digesters were able to form struvite if solution pH was increased by ≤1 pH unit. Depending on the WWTP, P recovery in filtrates through struvite precipitation ranged from 27–57% by mass at pH 8.5, via NaOH additions or air sparging. Increasing filtrate Mg concentrations improved P recovery up to 97%. Based upon these results, small WWTPs using aerobic digestion will be able to lower their P waste output through recovery as struvite fertilizer.

Keywords: activated sludge; aerobic digestion; phosphorus; struvite; wastewater treatment plant (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2019
References: View complete reference list from CitEc
Citations: View citations in EconPapers (4)

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