The recovery of phosphorus
(P) from high-strength acidic waste
streams with high salinity and organic loads is challenging. Here,
we addressed this challenge with a recently developed electrochemical
approach and compared it with the chemical precipitation method via
NaOH dosing. The electrochemical process recovers nearly 90% of P
(∼820 mg/L) from cheese wastewater in 48 h at 300 mA with an
energy consumption of 64.7 kWh/kg of P. With chemical precipitation,
>86% of P was removed by NaOH dosing with a normalized cost of
1.34–1.80
euros/kg of P. The increase in wastewater pH caused by NaOH dosing
triggered the formation of calcium phosphate sludge instead of condensed
solids. However, by electrochemical precipitation, the formed calcium
phosphate is attached to the electrode, allowing the subsequent collection
of solids from the electrode after treatment. The collected solids
are characterized as amorphous calcium phosphate (ACP) at 200 mA or
a precipitation pH of ≥9. Otherwise, they are a mixture of
ACP and hydroxyapatite. The products have sufficient P content (≤14%),
of which up to 85% was released within 30 min in 2% citric acid and
a tiny amount of heavy metals compared to phosphate rocks. This study
paves the way for applying electrochemical removal and recovery of
phosphorus from acidic P-rich wastewater and offers a sustainable
substitute for mined phosphorus.