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Applications of Ozone Micro- and Nanobubble Technologies in Water and Wastewater Treatment: Review
Andinet Tekile,Ilho Kim,Jai-Yeop Lee 대한상하수도학회 2017 상하수도학회지 Vol.31 No.6
Water and wastewater treatment has always been a challenging task due to the continuous increase in amount and the change in characteristics of the poorly biodegradable and highly colored organic matters, as well as harmful micro-organisms. Advanced techniques are therefore required to successfully remove these pollutants from water before reuse or discharge to receiving water bodies. Application of ozone, which is a powerful oxidant and disinfectant, alone or as part of advanced oxidation process depends on the complex kinetic reactions and the mass transfer of ozone involved. Micro- and nano bubbling considerably improves gas dissolution compared to conventional bubbles and hence mass transfer. It can also intensify generation of hydroxyl radical due to collapse of the bubbles, which in turn facilitates oxidation reaction under both alkaline as well as acidic conditions. This review gives the overview of application of micro- and nano bubble ozonation for purification of water and wastewater. The drawbacks of previously considered techniques and the application of the hydrodynamic ozonation to synthetic aqueous solutions and various industrial wastewaters are systematically reviewed.
Extent and persistence of dissolved oxygen enhancement using nanobubbles
Andinet Tekile,Ilho Kim,Jai-Yeop Lee 대한환경공학회 2016 Environmental Engineering Research Vol.21 No.4
In this study, change in water-dissolved oxygen (DO) was analyzed under various synthetic water qualities and nanobubbles (NBs) application conditions, such as gas type, initial DO as well as water dissolved, suspended and organic matters contents. When oxygen, rather than air, was introduced into nitrogen-desorbed ultra-pure water, the stagnation time was significantly increased. It took ten days for DO concentration to drop back to saturation. The higher the initial DO concentration, the longer particles were observed above saturation due to particle stability improvement. The oxygen mass transfer rate of 0.0482 mg/L/min was found to reach a maximum at an electrolytic concentration of 0.75 g/L, beyond which the transfer rate decreased due to adsorption of negative ions of the electrolyte at the interface. High levels of turbidity caused by suspended solids have become a barrier to dissolution of NBs oxygen into the water solution, and thus affected the transfer performance. On the other hand, by applying NBs for just an hour, up to 7.2% degradation of glucose as representative organic matter was achieved. Thus, NBs technology would maintain a high DO extent for an extended duration, and thus can improve water quality provided that water chemistry is closely monitored during its application.
수류확산과 초음파와 오존을 이용한 현장 수질 개선 평가
테킬안디넷 ( Andinet Tekile ),김일호 ( Ilho Kim ),이재엽 ( Jai-yeop Lee ) 한국물환경학회(구 한국수질보전학회) 2017 한국물환경학회지 Vol.33 No.2
This study used jet water flow, ultrasonication, and ozonation units to investigate the impact of the unit components on the water quality of the stagnant Yeo-cheon River in Korea. Samples were collected at six locations, before the experiment and at 1, 3, and 6 hrs afterward. By operating the water-flow unit only, dissolved oxygen increased by as much as 90% after 3 hrs, 25 m downstream from the device, and Chi-a was reduced by 80%. With sonication added, more than 80% of the ChI-a was removed, even at 100 m downstream from the device. In addition, total dissolved phosphorus was reduced from an average value of 420 (± to μg/L before ultrasonic irradiation to 160 (±40) \μ/L afterward. By releasing ozone into the flow with sonication, ChI-a was greatly removed from the water column, and ammonia nitrogen also decreased, to an average value of 20 n column 60 μg/L. However, because only 3*10-3 mg/L of ozone was used for safety reasons, and because of its brief reaction time, the effect of integrating ozone into the system covered only a small area. Generally, combining sonication with jet flow is promising for preventing algal bloom formation, because it effectively removed Chi-a from the water column.