Optimising a novel SBR configuration for enhanced biological phosphorus removal and recovery (EBPR²)

© 2017 Desalination Publications. All rights reserved. This work proposes a new SBR configuration to recover P from the water line: enhanced biological phosphorus removal and recovery (EBPR2). The main objective is evaluating its feasibility using modelling techniques in view of its optimization. The new EBPR2 configuration adds an anaerobic settling phase to the classical anaerobic/aerobic sequence to obtain an anaerobic/settling/aerobic/ settling cycle. Part of the anaerobic supernatant with high P content is extracted from the SBR and a chemical P-precipitation unit will be in charge of recovering it. The optimal operation is obtained for an anaerobic supernatant extraction of 4.3% of the total volume per cycle. The system is stable and accomplishing COD, N and P discharge limits for any VFA/Total COD ratio in the influent and for sludge retention time higher than 4 d. More than 60% of the P in the influent can be recovered. Lower COD is required than in the classical configuration. The system works with similar amount of PAO but with lower polyphosphate content, which provides a more resilient configuration. In addition, solids are wasted after the anaerobic phase with three times the internal PHA content compared to the classical aerobic purge, improving the chances to recover and valorise this bioplastic.