Struvite Phosphorus Recovery from Aerobically Digested Municipal Wastewater

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 (MgNH4PO4·6H2O) 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 m3 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.

Corn and soybean response to wastewater‐recovered and other common phosphorus fertilizers

“…Furthermore, if the removal and reuse of nutrients from wastewater was fully implemented on a national level, the U.S. demand for RP could be reduced by 20% (Hallas et al, 2019).…”

Holistic Approach to Phosphorus Recovery from Urban Wastewater: Enhanced Biological Removal Combined with Precipitation

“…Similar recovery values were also observed for struvite precipitation from aerobically digested sludge filtrates from four small WWTPs in north Florida (USA), ranging from 41%-61% recovered P, which could be improved to over 90% by Mg salt additions. In that case study, however, WWTP-wide P-load reduction estimates ranged only from 3%-43% as these facilities did not rely on EBPR in the treatment train [26].…”

Investigation of struvite crystals formed in palm oil mill effluent anaerobic digester

“…For example, in swine farming industry, struvite precipitation of its wastewater was explored with the purpose to remove ammonia nitrogen and simultaneously recover phosphate from its wastewater stream ( Huang et al., 2016 ) ( Taddeo et al., 2016 ). In dairy and municipal wastewater also, several works were done with the aim to recover phosphate mineral repurposing it to be alternative mineral fertilizer ( Aleta et al., 2018 ; Hallas et al., 2019 ).…”