Multi-Method analysis including 57Fe Mössbauer Spectroscopy to quantify vivianite for phosphorus recovery in real wastewater environments

Abstract

Phosphorus recovery from wastewater is increasingly vital due to its limited availability and essential role in food production. This study investigates the formation and quantification of vivianite, a promising pathway for phosphorus recovery, in Viikinmäki wastewater treatment plant (WWTP) in Helsinki, Finland, utilizing a combination of ⁵⁷Fe Mössbauer spectroscopy at 300.0 K and 5.6 K, X-ray diffraction (XRD), and chemical analysis. The study revealed the strengths and limitations of Mössbauer spectroscopy, using the multi-method analysis. The findings highlight the effectiveness of Mössbauer spectroscopy in distinguishing vivianite from other rarely discussed iron phases such as siderite and ferrihydrite. XRD confirmed the presence of crystalline phases, while chemical analysis provided a clear differentiation between Fe²⁺ and Fe³⁺, crucial for distinguishing vivianite Fe³⁺ from other components. Single approaches for estimating the recovery potential of phosphorus were compared. These methods had the tendency to overestimate the amount of phosphorus that can be recovered as vivianite. However, the multi-method analysis provided the most realistic balanced estimates. Practical recommendations are offered to WWTP operators to monitor the enhancement of phosphorus recovery efficiency, complying with evolving stringent regulations, and optimizing coagulant dosing. This comprehensive approach bridges the gap between academic research and real-world application, promoting sustainable wastewater management practices.