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This research demonstrates the assessment of the removal efficiency of organic matter, nitrogen, and phosphorus in wastewater of Phu Bai industrial zone using aerobic granular sludge process in sequential batch reactor (SBR). The experiment was carried out in two SBR namely R1 and R2 with 240 minutes of cycle time and a two-stepwise aeration was applied including 90 minutes at airflow rate Q1=6 L/min and 136 minutes at Q2=2 L/min. However, one-step feeding was used for R1, meanwhile, 2-step feeding (75% of volumetric at the beginning of batch and 25% remaining after aeration time Q1) was applied for R2. The result showed that the size of sludge particle has increased from 1 to 2 mm and high biomass (in Total Suspended Solid (TSS) of g/L was retained in both reactors and sludge shows a good settling ability with a low SVI value of 40-42 mL/g TSS after 50 days of operational experiment. It was indicated that aerobic granular sludge in R1 and R2 still maintained the development and stability during the operation. The removal efficiency of COD and N-NH4+ removal in two reactors were similar and kept high at 92-93 and 96-97%, respectively, while P-PO43- removal efficiency was just in the range of 68-80%. The simultaneous nitrification and denitrification process (SND) was achieved with two-stepwise aeration in both reactors. Additionally, the experimental data showed the efficiency of SND in R2 (85-87%) was higher than that of R1 (64-68%), which demonstrated that the operating mode in R2 was more effective to treat organic matter and nitrogen in SBR operation. Furthermore, the higher efficiency of SND in R2 in comparison with R1 also leads to 10-13% higher in removal efficiency of total nitrogen between R2 (75-78%) and R1 (68-69%). However, both operating modes still did not reach the complete removal of total nitrogen in the reactor.
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