Recovery of phosphorus and volatile fatty acids from wastewater and food waste with an iron-flocculation sequencing batch reactor and acidogenic co-fermentation

- Fe(III) dosing at 25 mg/L for SBR increases the P removal to more than 95%.
- Co-fermentation of P-rich sludge with food waste facilitates P release into solution.
- Co-fermentation of food waste in the side-stream produces VFAs as organic resource.
- P can be effectively recovered by re-precipitation with Fe(II) to form vivianite.

A sequencing batch reactor-based system was developed for enhanced phosphorus (P) removal and recovery from municipal wastewater. The system consists of an iron-dosing SBR for P precipitation and a side-stream anaerobic reactor for sludge co-fermentation with food waste. During co-fermentation, sludge and food waste undergo acidogenesis, releasing phosphates under acidic conditions and producing volatile fatty acids (VFAs) into the supernatant. A few types of typical food waste were investigated for their effectiveness in acidogenesis and related enzymatic activities. The results show that approximately 96.4% of total P in wastewater was retained in activated sludge. Food waste with a high starch content favoured acidogenic fermentation. Around 55.7% of P from wastewater was recovered as vivianite, and around 66% of food waste loading was converted into VFAs. The new integration formed an effective system for wastewater treatment, food waste processing and simultaneous recovery of P and VFAs.

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