Exploring the stability of an A-stage-EBPR system for simultaneous biological removal of organic matter and phosphorus

This work evaluates the performance and stability of a continuous anaerobic/aerobic A-stage system with in-tegrated enhanced biological phosphorus removal (A-stage-EBPR) under different operational conditions. Dis-solved oxygen (DO) in the aerobic reactor was tested in the 0.2-2 mgDO/L range using real wastewater amended with propionic acid, obtaining almost full simultaneous COD and P removal without nitrification in the range 0.5-1 mgDO/L, but failing at 0.2 mgDO/L. Anaerobic purge was tested to evaluate a possible mainstream P-recovery strategy, generating a P-enriched stream containing 22% of influent P. COD and N mass balances indicated that about 43% of the influent COD could be redirected to the anaerobic digestion for methane pro-duction and 66% of influent NH4+-N was discharged in the effluent for the following N-removal B-stage. Finally, when the system was switched to glutamate as sole carbon source, successful EBPR activity and COD removal were maintained for two months, but after this period settleability problems appeared with biomass loss. Mi-crobial community analysis indicated that Propionivibrio, Thiothrix and Lewinella were the most abundant species when propionic acid was the carbon source and Propionivibrio was the most favoured with glutamate. Thiothrix, Hydrogenophaga, Dechloromonas and Desulfobacter appeared as the dominant polyphosphate-accumulating or-ganisms (PAOs) under different operation stages.

Automated summary

This study evaluates the performance and stability of a continuous anaerobic/aerobic A-stage system with integrated enhanced biological phosphorus removal (A-stage-EBPR) under different operational conditions. The results show that COD and P removal can be achieved simultaneously in the aerobic reactor, within a certain range of dissolved oxygen (DO) levels. Anaerobic purge can be used as a possible mainstream P-recovery strategy. The switch to glutamate as sole carbon source maintains successful EBPR activity and COD removal for two months, but settleability problems and biomass loss occur afterwards.