• Membrane and Water Treatment
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• v.10 no.4
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• pp.307-311
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• 2019

The ejector type microbubble generator, which is the method to supply air to water by using cavitation in the nozzle, does not require any air supplier so it is an effective and economical. Also, the distribution of the size of bubbles is diverse. Especially, the size of bubbles is smaller than the bubbles from a conventional air diffuser and bigger than the bubbles from a pressurized dissolution type microbubble generator so it could be applied to the aeration tank for wastewater treatment. However, the performance of the ejector type microbubble generator was affected by hydraulic pressure and MLSS(Mixed Liquor Suspended Solid) concentration so many factors should be considered to apply the generator to aeration tank. Therefore, this study was performed to verify effects of hydraulic pressure and MLSS concentration on oxygen transfer of the ejector type microbubble generator. In the tests, the quantity of sucked air in the nozzle, dissolved oxygen(DO) concentration, oxygen uptake rate(OUR), oxygen transfer coefficient were measured and calculated by using experimental results. In case of the MLSS, the experiments were performed in the condition of MLSS concentration of 0, 2,000, 4,000, 8,000 mg/L. The hydraulic pressure was considered up to $2.0mH_2O$. In the results of experiments, oxygen transfer coefficient was decreased with the increase of MLSS concentration and hydraulic pressure due to the increased viscosity and density of wastewater and decreased air flow rate. Also, by using statistical analysis, when the ejector type microbubble generator was used to supply air to wasterwater, the model equation of DO concentration was suggested to predict DO concentration in wastewater.

• Journal of the Korea Organic Resources Recycling Association
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• v.24 no.4
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• pp.31-37
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• 2016

This study was conducted to investigate the effect of OH radicals on organic matter oxidation and suspended solids removal using microbubble as a pre-treatment technique to reduce the organic load of night soil in connection with sewage. The experiment was conducted for three months at HRT 4 hours using pressurized type microbubble generator. The mean SS removal efficiency was achieved 71%. The average removal efficiency of $TCOD_{Cr}$, TBOD, TN and TP were achieved for 51.5%, 47.9%, and 14.7% respectively, as scum and SS were removed by flotation separation. The removal efficiency of soluble organic matters were 25.0%, 17.1% for $SCOD_{Cr}$, SBOD by air microbubble supply. Soluble nitrogen and phosphorus were removed average of 11.9% and 7.4%, respectively. As s result, it was confirmed that soluble organic matters were removed by air microbubble supplied. Generated OH radicals when the microbubble was collapsed, can decompose the soluble organic matters. Therefore, The microbubble flotation process was installed at the front of night soil treatment process, it will contribute to the stable operation of the subsequent biological treatment facility by oxidation of the dissolved organic matters as well as removal of SS by flotation separation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.9
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• pp.6397-6402
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• 2015

This research was performed to review operating parameters, optimum condition and check characteristic of microbubble generation for using bubble size distribution according to venturi specification. Optimum operating condition have airflow rate 0.3 LPM, 3 bar(pressure tank) and connecting nozzle directly(without valve), it is advantageous to generate microbubble. In case of characteristic of microbubble generation according to venturi specification, effect that nozzle specification affects bubble size distribution is low impact. But considering performance aspects, when using nozzle that throat diameter 3-4 mm, $D_{50}$ are $54.98-61.19{\mu}m$(D3L15, D4L15), fraction of bubble less than $50{\mu}m$ are 0.326, 0.345. And it is superior to others. Besides, $D_{50}$ and fraction of bubble less than $50{\mu}m$ of throat length 20 mm are $49.40-54.98{\mu}m$, 0.447, respectively And nozzle that throat length 20 mm is relatively tendency to generate microbubble stably.