49 / 2023-05-04 10:41:42

Mechanisms and comprehensive regulation of phosphorous recovery and methane production in the anaerobic digestion system

Phosphorus recovery,Sewage sludge,Iron(III) reduction,Anaerobic digestion,Vivianite,Methane production

Recovering phosphorus from secondary sources like municipal wastewater and sludge, considered the promising P-rich stream, has aroused much attention due to global phosphorus scarcity. Crystallization of P as possible fertilizer is one of the feasible ways to meet the goal. Phosphorous crystallization in the form of vivianite (Fe₃(PO₄)₂·8H₂O) from sludge has been widely investigated out of practical and economic considerations. Usually, iron is added to the sludge system to achieve the ideal Fe/P molar ratio (1.5 or higher) for better vivianite formation. However, the effects of ambient species and concentrations of iron-phosphorus compounds (FePs) impose a great influence on the release of phosphorus from the solid phase into the supernatant. Moreover, in the process of simultaneous iron reduction and methanogenesis, the evolution mechanism of dissimilatory iron-reducing bacterium (DIRB) and methanogens community driven by added iron source remains largely unclear. In this study, batch experiments using thermal hydrolyzed sludge with different iron resources and dosages were carried out. Through the distribution of Fe/P, and changes in the microbial community before and after the Fe addition, the underneath mechanisms of iron(III) reduction-induced phosphate precipitation and methane production in the anaerobic digestion process is clarified, and therefore facilitate the comprehensive regulation of phosphorus recovery efficiency and the methanogenesis rate.

Recovering phosphorus from secondary sources like municipal wastewater and sludge, considered the promising P-rich stream, has aroused much attention due to global phosphorus scarcity. Crystallization of P as possible fertilizer is one of the feasible ways to meet the goal. Phosphorous crystallization in the form of vivianite (Fe₃(PO₄)₂·8H₂O) from sludge has been widely investigated out of practical and economic considerations. Usually, iron is added to the sludge system to achieve the ideal Fe/P molar ratio (1.5 or higher) for better vivianite formation. However, the effects of ambient species and concentrations of iron-phosphorus compounds (FePs) impose a great influence on the release of phosphorus from the solid phase into the supernatant. Moreover, in the process of simultaneous iron reduction and methanogenesis, the evolution mechanism of dissimilatory iron-reducing bacterium (DIRB) and methanogens community driven by added iron source remains largely unclear. In this study, batch experiments using thermal hydrolyzed sludge with different iron resources and dosages were carried out. Through the distribution of Fe/P, and changes in the microbial community before and after the Fe addition, the underneath mechanisms of iron(III) reduction-induced phosphate precipitation and methane production in the anaerobic digestion process is clarified, and therefore facilitate the comprehensive regulation of phosphorus recovery efficiency and the methanogenesis rate.