Simultaneous nitrogen and phosphorus removal from simulated digested piggery wastewater in a single-stage biofilm process coupling anammox and intracellular carbon metabolism.

A Single-stage biofilm process coupling Anammox and Intracellular Carbon metabolism (SAIC) was constructed for treating simulated digested piggery wastewater with low carbon/nitrogen ratio (C/N) in this study. TN removal in SAIC system increased by more than 12.77% compared to the reference, and the maximum total phosphorus (TP) removal efficiency reached to 83.70% (C/N = 1.5). Denitrification driven by intracellular carbon, mainly poly-β-hydroxybutyrate (PHB, 78.57%), contributed 32.60% of TN elimination at most, and at least 67.40% should be attributed to anammox. Phosphorus was thought to be mainly removed through biological route, while chemical precipitation also explained around 10% of removed TP. Furthermore, commensalism of glycogen accumulating organisms (GAOs), phosphate accumulating organisms (PAOs), nitrifiers and anammox bacteria was revealed by combining 16S rRNA amplicon sequencing and metagenomics. As a result, multiple metabolic pathways including anammox, (partial) nitrification, endogenous (partial) denitrification and biological P-removal played synergistic effect in SAIC system.