Anaerobic ammonium oxidation (anammox) coupled with hydroxyapatite (HAP) crystallization not only achieves simultaneous nitrogen removal and phosphorus recovery, but also cultivates excellent anammox granules. However, a floatation and wash-out of anammox-HAP granules was occurred at low phosphate concentrations. In this study, a reactor inoculated with mature anammox-HAP granules and fed with low phosphate (5 mg P/L) was added with granular activated carbon (GAC) to maintain sludge granulation and nitrogen-removing stability. At influent total nitrogen >800 mg/L and nitrogen loading rate ~ 9.8 kg/m³/d, a satisfactory nitrogen removal of around 88% was maintained during 140 days of operation. Insufficient phosphate supplement resulted in a sludge bulking, with suspended solid and sludge density decreased whereas sludge water content and expansion ratio increased due to HAP loss. Nevertheless, the sludge re-granulation was found at the later stage as the proportion of granules in 2.8– 3.35 mm went up to 37.4% after large granules disintegrated into small pieces at the initial stage. The settling velocity was finally ranging from 129.8 to 182.2 m/h. In addition, Candidatus Brocadia was increased from 2.1% to 20.1% and dominated in the microbial community. These findings suggest GAC was able to promote re-granulation of anammox-HAP granules at low phosphate concentration, which avoids sludge flotation and widens their application as an inoculum.

厌氧氨氧化（anammox）结合羟基磷灰石（HAP）结晶不仅实现了脱氮磷回收的同步，而且培养出优良的厌氧氨颗粒。然而，在低磷酸盐浓度下发生了厌氧氨氧化-HAP 颗粒的漂浮和冲洗。在这项研究中，一个反应器接种了成熟的厌氧氨氧化 HAP 颗粒并加入低磷酸盐 (5 mg P/L)，加入颗粒活性炭 (GAC)，以保持污泥颗粒化和脱氮稳定性。在进水总氮 >800 mg/L 和氮负载率 ~ 9.8 kg/m ^{3 时}/d，在 140 天的运行期间，令人满意的脱氮率保持在 88% 左右。磷酸盐补充不足导致污泥膨胀，悬浮物和污泥密度降低，而由于HAP损失，污泥含水量和膨胀率增加。然而，在后期发现污泥重新造粒，2.8-3.35 mm 的颗粒比例在初始阶段大颗粒分解成小块后上升到 37.4%。沉降速度最终在 129.8 至 182.2 m/h 的范围内。此外，候选人Brocadia 从 2.1% 增加到 20.1%，并在微生物群落中占主导地位。这些发现表明 GAC 能够在低磷酸盐浓度下促进 anammox-HAP 颗粒的再造粒，从而避免污泥浮选并扩大其作为接种物的应用。