Long-term effects of phosphorus deficiency on one-stage partial nitrification-anammox system and recovery strategies

Abstract

Long-term treatment of phosphorus-deficient wastewater using a one-stage partial nitrification-anammox (PNA) process may affect the growth of functional bacteria. A 650-day experiment on reject water with total phosphorus (TP)≤0.2 mg/L was conducted, using a lab-scale PNA system. The experiment found that long-term phosphorus deficiency led to a significant decrease in nitrogen removal efficiency (NRE) (91.0–28.3%), a high sludge volume index (SVI) of 157.6 mL/g-MLSS and sludge bulking. The abundance of hzsA in flocs decreased from 3.18 ± 0.05 × 106 to 1.10 ± 0.10 × 106 copies/mg-VSS. The biofilm had an advantage in resisting phosphorus deficiency with hzsA abundance being 3.78 ± 0.04 × 106 copies/mg-VSS at its lowest. According to batch test results, 0.2 mg/L PO43--P was added to the reactor. After 50 days, nitrogen removal rate (NRR) achieved up to 0.35 kg-N/(m3-d) at nitrogen load rate (NLR) of 0.4 kg-N/(m3-d) (NRE: 87.8%), and sludge bulking disappeared (SVI was 98.8 mL/g-MLSS). This experiment can serve as a reference for PO43--P dosing when using the PNA process to treat phosphorus-deficient wastewater.