Efficient carbon, nitrogen and phosphorus removal from low C/N real domestic wastewater with aerobic granular sludge

This work reports on simultaneous nitrification, denitrification and phosphorus removal treating real domestic wastewater with low carbon/nitrogen (C/N) ratio by aerobic granular sludge (AGS). Operations at high sludge retention time (SRT = 61 ± 24 days) resulted in low biomass yield per chemical oxygen demand removed (COD_rem) (0.21 ± 0.01 gCOD_x/gCOD_rem), lower COD demand for denitrification as well as high effluent quality in terms of total suspended solids (TSS) (22 ± 7 mgTSS/L). The average ratio between the biodegradable soluble COD stored anaerobically as polyhydroxyalkanoates (PHAs) and the N removed was 3.1 ± 0.6 gCOD_sto/gN_rem, suggesting that nitrification/denitrification occurred partly via the nitrite pathway. Results revealed that stable AGS process with high C/N/P removal efficiency of 84/71/96% can be obtained besides a low organic loading rate (0.43 ± 0.11 g COD/L/d) and influent C/N ratio (3.8 ± 1.6 g/g), resulting in a high effluent quality characterized by 25 ± 6 mg sCOD/L, 0.09 ± 0.07 mgPO₄-P/L, 9 ± 2 mgTIN/L (10 ± 2 mgTN/L) and 22 ± 7 mgTSS/L.