Staggered supply of ferric citrate and oxygen as electron acceptors promote the co-recovery of vivianite and bioplastics PHB from wastewater

• Increasing and segmented Fe 3+ electron acceptor dosage enhanced vivianite recovery • Fe 3+ sole electron acceptor addition had no advantage in PHB accumulation • Staggered supply of Fe 3+ and O 2 facilitated co-recovery of vivianite and PHB • The staggered supply of dual electron acceptors enriched PHB-producing bacteria Biodegradable bioplastic polyhydroxyalkanoate (PHA) produced and recovered from wastewater offered an effective strategy to replace synthetic plastics while mitigating plastics waste pollution. In addition to the recovery of high-value organic products like PHA, the synthesis of vivianite mineral from wastewater demonstrated great potential as a highly effective method for phosphorus recovery. To facilitate the co-recovery of vivianite and PHA, we investigated the staggered supply of ferric citrate and oxygen as dual electron acceptors, aiming to enhance the concurrent recovery of high-value organics and phosphorus. When 6 mM of ferric citrate was used as the sole electron acceptor, the vivianite recovery increased from 34% with one single dose of the electron acceptor to 49% with twice the dose. Simultaneously, the yield of polyhydroxybutyrate (PHB), a typical PHA, was only 0.17 g PHB/g COD HAc. However, when ferric citrate and oxygen were used as dual electron acceptors, the vivianite formation efficiency was stabilized at 50%. Simultaneously, the PHB yield boosted to 0.79 g PHB/g COD HAc, 3.6 times higher than with ferric citrate as sole electron acceptor and significantly exceeding that in previous studies using oxygen alone. PHB-producing bacteria, including Candidatus Competibacter, Paracoccus , and Thauera , were effectively enriched through the staggered supply of the dual electron acceptors. As a result, the staggered supply of dual electron acceptors represented an efficient and sustainable method for the co-recovery of PHB and vivianite from wastewater.