Benefits and drawbacks of integrating a side-stream sludge fermenter into an A2O system under limited COD conditions

The implementation of a side-stream sludge fermenter (SSSF) has been identified as a possible solution to improve the performance of an anaerobic/anoxic/aerobic (A2O) configuration when treating low COD waste-water. This study systematically evaluated the effects of incorporating a SSSF into an A2O configuration (side -stream enhanced biological phosphorus removal, S2EBPR) for P/N/COD removal under a limited influent COD (CODINF) condition. The performance of the S2EBPR (with the SSSF receiving 6% of the recycled activated sludge and operating with a hydraulic retention time (HRT) of 2.4 d) and A2O were compared under the same limited CODINF (350 mg/L) condition. S2EBPR improved the amount of P removed (26.6%) under a low influent COD/P of only 26.3 compared with A2O of 32.6, and enhanced denitrification (11%) without compromising full ammonium and COD removal. However, the PLOAD to the plant increased due to the P-release in SSSF, resulting in higher effluent P concentration. The methane and energy recovery indexes were around 45% lower than those of A2O. Sequencing analysis revealed a high abundance of PAO in accordance to its higher P removal. This study represents a comprehensive evaluation of the S2EBPR configuration and provides an assessment of its suitability.

Automated summary

This study evaluates the effects of incorporating a side-stream sludge fermenter (SSSF) into an anaerobic/anoxic/aerobic (A2O) configuration for P/N/COD removal under a limited influent COD condition. The results show that the S2EBPR configuration improves P removal but also increases P-release, leading to higher effluent P concentration.