생물학적 질산화시 폭기효율 개선을 위한 나선형반응조 개발 및 미생물 군집해석
- 생물학적 질산화시 폭기효율 개선을 위한 나선형반응조 개발 및 미생물 군집해석
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- The aerobically biological process has a problem which causes high energy-costs by aeration through treating high-strength pollutants, which requires the improvement of aeration efficiency in the process. This study was conducted for the development of new reactor (Spiral reactor) in order to enhance oxygen transfer through increasing the retention time of air bubble in liquid phase induced to spiral air-flow. The efficiency of Spiral reactor was verified in pure water and biological wastewater treatment system in which the bioreactor was operated in lab-scale and pilot-scale and compared with Control reactor without spiral structure.
In pure water, oxygen transfer coefficient (KLa) of Spiral reactor comprising the structure with 5 turns of spirals was estimated to 47% higher than that of Control reactor (i.e. 0.08 vvm of air flow rate as low aeration). In lab-scale Spiral bioreactor operation treating the swine wastewater anaerobically digested, over 99.9% of 300 NH4+-N mg/L in the wastewater was removed and complete nitrification was achieved in SBR process. In ammonia oxidation, 2.7 days and 1.9 days was required, in nitrite oxidation, 4.8days and 4.8 days required in Control and Spiral reactor, respectively. And the saving aeration of Spiral reactor was confirmed about 25% compared to that of Control reactor. In the SBR process, as batch reaction got performed consecutively (SBR 1~4), the nitrification rate was faster more and more (i.e. 2.4 times faster in ammonia oxidation and 1.4 times faster in nitrite oxidation in Spiral reactor). In addition, the nitrification rate of Spiral reactor was about 1.3 times faster than that of Control reactor, which was assumed to be caused by microbial attachment such as biofilm under surface of the structure in Spiral reactor. During the consecutive batch, the dominant cluster in AOB community was shifted from Nitrosomonas cryotolerans to Nitrosomonas europaea in SBR 1 and this dominance by Nitrosomonas europaea cluster maintained and increased after SBR 1. Likewise, the dominant genus in NOB community was also shifted from Nitrospira to Nitrobacter. These results were assumed that the change of environment about substrate concentration by treating high-strength ammonia caused the dominant group to shift from k-strategist to r-strategist. And furthermore, the increased portion and number of r-strategist species or genus contribute the nitrification rate to be faster during the consecutive SBRs. In pilot-scale operation of Spiral reactor aerated 25% and 50% less than Control reactor (based on lab-scale results), complete nitrification was achieved presenting almost identical performance with Control reactor (about 10% of standard deviation about the nitrification rates). It provided the possibility of practical application of Spiral reactor through process scale-up with high aeration-efficiency.
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