| Summary: | 碩士 === 淡江大學 === 水資源及環境工程學系碩士班 === 102 === Nitrification of aerobic granules cultivated by high pressure reactor (HP) (3 kg/cm2) is better than that of aerobic granules cultivated by ambient pressure reactor (AP). Aerobic granules cultivated by HP reactor reached partial nitrification, i.e., oxidation of ammonium to nitrite, in the short period of time after HP reactor being commenced. Under various ammonium loading rates, ammonium removal efficiency of 92% can be reached. Accumulation of nitrifying bacteria in AP reactor is not as effective as that in HP, and longer time is needed for aerobic granules cultivated by AP reactor to reach partial nitrification. The granule size of aerobic granules cultivated by AP reactor is bigger than that of aerobic granules cultivated by HP reactor. Aerobic granules cultivated by AP reactor show simultaneous nitrification– denitrification (SNDN) capability. TN removal efficiency of 32.0±10.3% could be reached by AP system.
To evaluate the capability of HP and AP for TN removal, a pre-anoxic step was integrated into the operation sequence, and both systems were restarted with new seeding sludges. Both systems were operated with low organic loading rate (OLR) of 2.2 kg COD/m3-day and C/N ratio of 3. Although, aerobic granules were not formed successfully in short period of time, the results show that TN is removed by biological nitrification/denitrification process and by assimilation into biomass with removal efficiency of above 93% for both of systems being reached. The reasons that aerobic granules did not form successfully might be due to disintegration of granules by the mechanical mixing during anoxic period. It is also possible that granules might contain N2 gas generated from denitrification process, resulting in flotation and washout of during discharge period.
Mechanical mixing was replaced with intermittent aeration by recycling air inside the reactor during anoxic period to reduce the destruction of aerobic granules, and both systems were restarted with new seeding sludges. Aerobic granules formed successfully for both systems. After 140-day operation, MLSS were 13.4 g/L and 7.93 g/L, and SVI30 were 24.6 mL/g and 39.1 mL/g, respectively, in HP and AP. TN is removed by pre-anoxic processes of HP system, Compared the two TN removal efficiency (34.0±15.6%, 43.4±5.8%) resulted from different C/NTON ratios (4～5, 10～12), system operated at the higher C/NTON ratios (10～12) is more stable and does not cause accumulation of total oxidized nitrogen (TON). Nitrification– denitrification doesn’t reach by AP system in the short period of time.
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