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This research studied integrated fixed film activated sludge (IFAS) technology to simultaneously remove N and P in real municipal wastewater by combining anammox biofilms with flocculent activated sludge for enhanced biological P removal (EBPR). The study was conducted in a sequencing batch reactor (SBR) operated as a conventional A2O (anaerobic-anoxic-oxic) process with an 8.8 h hydraulic retention time. After achieving steady-state operation, the reactor showed robust performance, with average removal efficiencies of 91.3±4.1% for total inorganic nitrogen (TIN) and 98.4±2.4% for phosphorus (P). Denitrifying polyphosphate accumulating organisms (DPAOs) were responsible for 15.9% of P uptake during the anoxic phase, while biofilms showed anammox activity in the aerobic step. The IFAS configuration with a low solid retention time (SRT) of 5 days prevented the washout of biofilm anammox bacteria and allowed selective washout of unwanted organisms. The results demonstrated the successful coexistence of anammox bacteria with other bacteria for efficient nutrient removal in real wastewater conditions. 

This research studied integrated fixed film activated sludge (IFAS) technology to simultaneously remove N and P in real municipal wastewater by combining anammox biofilms with flocculent activated sludge for enhanced biological P removal (EBPR). The study was conducted in a sequencing batch reactor (SBR) operated as a conventional A2O (anaerobic-anoxic-oxic) process with an 8.8 h hydraulic retention time. After achieving steady-state operation, the reactor showed robust performance, with average removal efficiencies of 91.3±4.1% for total inorganic nitrogen (TIN) and 98.4±2.4% for phosphorus (P). Denitrifying polyphosphate accumulating organisms (DPAOs) were responsible for 15.9% of P uptake during the anoxic phase, while biofilms showed anammox activity in the aerobic step. The IFAS configuration with a low solid retention time (SRT) of 5 days prevented the washout of biofilm anammox bacteria and allowed selective washout of unwanted organisms. The results demonstrated the successful coexistence of anammox bacteria with other bacteria for efficient nutrient removal in real wastewater conditions. 

The mainstream application of anaerobic ammonium oxidation (anammox) for sustainable N removal remains a challenge. Similarly, with recent additional stringent regulations for P discharges, it is imperative to integrate N with P removal. This research studied integrated fixed film activated sludge (IFAS) technology to simultaneously remove N and P in real municipal wastewater by combining biofilm anammox with flocculent activated sludge for enhanced biological P removal (EBPR). This technology was assessed in a sequencing batch reactor (SBR) operated as a conventional A2O (anaerobic-anoxic-oxic) process with a hydraulic retention time of 8.8 h. After a steady state operation was reached, robust reactor performance was obtained with average TIN and P removal efficiencies of 91.3 ± 4.1% and 98.4 ± 2.4%, respectively. The average TIN removal rate recorded over the last 100 d of reactor operation was 118 mg/L⋅d, which is a reasonable number for mainstream applications. The activity of denitrifying polyphosphate accumulating organisms (DPAOs) accounted for nearly 15.9% of P-uptake during the anoxic phase. DPAOs and canonical denitrifiers removed approximately 5.9 mg TIN/L in the anoxic phase. Batch activity assays, which showed that nearly 44.5% of TIN were removed by the biofilms during the aerobic phase. The functional gene expression data also confirmed anammox activities. The IFAS configuration of the SBR allowed operation at a low solid retention time (SRT) of 5-d without washing out biofilm ammoniumoxidizing and anammox bacteria. The low SRT, combined with low dissolved oxygen and intermittent aeration, provided a selective pressure to washout nitrite-oxidizing bacteria and glycogen-accumulating organisms, as relative abundances.