The effect of substrate composition on the nutrient removal potential of sequencing batch reactors

Experimental results suggest that sequencing batch reactors (SBR) are not efficient for enhanced biological phosphorus removal from domestic sewage with low/medium organic carbon content when denitrification preferentially competes for available carbon. Total COD is not a meaningful parameter to reflect available substrate for N and P removal; COD fractionation and identification of the readily biodegradable COD fraction are required for an accurate assessment of system performance. The degree of soluble COD removal in the non-aerated phase is observed to be much higher than what may be calculated from stoichiometric relationships for N removal and P release, indicating the existence of competing mechanisms such as organic carbon storage by non-polyP bacteria under anaerobic conditions.