Single-stage C-N-P removal and ultra-low net sludge production driven by cyclic oxygen exposure and side-stream acidogenesis in an intermittent-aeration IFAS-OSA system.

O emissions (0.9% EF) were markedly below values typically reported for IA systems. Observed net sludge yields remained exceptionally low (0.09-0.20 gTSS/gCOD), significantly outperforming conventional and other OSA-based biological systems. The sludge exhibited good dewaterability (nCST 4-6 s·L/gTSS), while settleability deteriorated especially under mesophilic and extended anoxic exposure, reflecting known trade-offs of OSA operation. Overall, the IA IFAS-OSA configuration provides an extremely compact, efficient, and straightforwardly retrofittable solution for mainstream wastewater treatment.