Lab-scale experiments were conducted to investigate the aerobic granular sludge process for simultaneous phosphorus (P) accumulation by chemical precipitation and biological nitrogen removal via nitrite. The P-rich granules were successfully incubated in a sequencing batch reactor, in which simultaneous nitrification-denitrification occurred via nitrite. The average diameter of the P-rich granules was 2.47 mm and the P content in granules was much higher than that in other granular systems with enhanced biological phosphorus removal process. Filamentous bacteria (genus Thiothrix) in the granules and the long sludge retention time (30 d) of the granular system played a crucial role in accumulation of precipitated phosphate. X-ray diffraction analysis, scanning electron microscopy coupled with energy dispersive X-ray and the experimental design using response surface methodology confirmed that the main mineral patterns in P-rich granules were Ca-Mg phosphate and whitlockite.
Keywords: ACP; AOB; BIPP; COD; Chemical precipitation; DGGE; DO; EBPR; EDX; Filamentous bacteria; HAP; MLSS; MLVSS; NOB; P-rich granules; PAOs; PCR; RSM; SBR; SND; SRT; SVI(30); SVI(5); Simultaneous nitrification–denitrification via nitrite; TN; TP; X-ray diffraction; XRD; ammonium oxidizing bacteria; amorphous calcium phosphate; biologically induced phosphate precipitation; chemical oxygen demand mgL(−1); denaturing gradient gel electrophoresis; dissolved oxygen mgL(−1); energy dispersive X-ray; enhanced biological phosphorus removal; hydroxyapatite; mixed liquor suspended solids mgL(−1); mixed liquor volatile suspended solids mgL(−1); nitrite oxidizing bacteria; phosphate accumulating organisms; polymerase chain reaction; response surface methodology; sequencing batch reactor; simultaneous nitrification–denitrification; sludge retention time d(−1); sludge volume index at 30minmLg(−1); sludge volume index at 5minmLg(−1); total nitrogen mgL(−1); total phosphorus mgL(−1).
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