Potassium ferrate pretreatment enhances short-chain fatty acid production and phosphorus recovery in co-fermentation system of waste activated sludge and corn stover

Developing efficient technologies to recover carbon (C) and phosphorus (P) from waste activated sludge (WAS) is crucial for promoting low-carbon development and addressing P resource shortages. This study proposes a potassium ferrate (PF) pretreatment method to enhance the co-fermentation of WAS and corn straw (CS), facilitating the efficient and stable recovery of short-chain fatty acids (SCFAs) and vivianite, while exploring the underlying mechanisms and potential applications of this approach. PF pretreatment effectively promoted WAS hydrolysis and increased CS bioavailability. SCFAs yield in the co-fermentation group reached 6410.4 mg/L, representing a 79.6 % increase. Efficient SCFAs production was achieved under a SRT of 4–5 days. In the system, SCFAs-consuming bacteria were reduced and SCFAs-producing fermentative genera, such as Paraclostridium , Terrisporobacter and Mobilitalea , were enriched. Additionally, the presence of Fe promoted the enrichment of the Clostridium genus, which is capable of both fermentation and Fe reduction. PF pretreatment enhanced the release of organic matter, thereby shortening the fermentation time. P recovery was effectively achieved through chemical acidification and precipitation techniques. Under optimal recovery conditions (Fe/P = 1.5, pH = 7, 300 rpm), the P recovery efficiency reached 81.6 %, with vivianite accounting for 68.2 %–71.8 %. This method provides a theoretical foundation and technical support for the effective utilization of WAS