This article aims to provide a state-of-the-art assessment of the research work carried out so far in microbubble-aided transport processes The different methods of microbubble generation and the properties of microbubble have been reported in this article The different components that constitute the microbubble are also discussed The characteristics of microbubble are pointed out The measuring methods of zeta potential in microbubble system are described This article provides an update of important research works in the microbubble technology This article also reports the important future research scope and their significance in the microbubble flow system For researchers, this article may be useful for further research in microbubble technology

Microbubble generation and microbubble-aided transport process intensification—A state-of-the-art report

Microbubble-based methods, in recent times, have been widely used for purification of water and wastewater. Microbubbles have several physicochemi- cal properties, which make them eminently suitable for wastewater treatment. In this review, these properties have been analyzed in detail from the perspective of appli- cation. Various types of microbubble generators and their operation principles have been discussed. The transport of gas into the aqueous phase has been explained, and the correlations to predict the volumetric mass transfer coef- ficient have been presented. Many practical applications using ozone, oxygen and air microbubbles, some of which are currently at various stages of commercialization, have been presented. Other important uses of microbubbles for wastewater treatment, namely, removal of fine solid particulate matter and oil, have also been discussed. In addition, directions for future research of microbubble technology and their potential applications have been identified.

Microbubble-aided water and wastewater purification: a review

Enhanced free-radical generation by shrinking microbubbles using a copper catalyst.

Degradation of phenol by the collapse of microbubbles.

The role of interface in microbubble ozonation of aromatic compounds

The flow characteristics and decomposition performance in the cocurrent upflow bubble column dispersed with micro-bubbles were experimentally examined. A micro-bubble generator was installed at the bottom of the column, and for comparison the sintered glass gas sparger was set at the lower part of the column.When milli-bubbles coexist with dispersed micro-bubbles, micro-bubbles disappear. This is considered because micro-bubbles are absorbed into the wake of milli-bubbles. The volumetric mass transfer coefficient is higher for micro-bubbles than for milli-bubbles, but the mass transfer coefficient is much lower for the former than for the latter. The apparent decomposition rate constant strongly depends on the volumetric coefficient. When the volumetric coefficient is higher, the rate constant of micro-bubbles is higher than that of milli-bubbles.

Flow Characteristics in Cocurrent Upflow Bubble Column Dispersed with Micro-Bubbles

For the phosphorus recovery from the excess sludge in the sewage treatment process, the decomposition of excess sludge by using ozone micro-bubbles was focused, and the influence of ozone micro-bubble on the foam behavior and the decomposition performance was examined. A cocurrent upflow bubble column with micro-bubble generator was used and the excess activated sludge was decomposed under the various conditions. The foam behavior was observed and the decomposition performance was measured.The foam behavior was quite different with the bubble size. When ozone micro-bubbles were dispersed, the ozone decomposition was much enhanced. As a result, the decomposition time and required amount of ozone became much lower than those in the case of milli-bubbles.

https://www.jstage.jst.go.jp/article/pmfr/3/0/3_0_51/_pdf

Influence of Micro-bubble on Ozone-Decomposition of Excess Sludge

炭化素材は生物的親和性を有しており，微生物の固定化に有効である．本研究では，硝化菌の固定化担体として炭化繊維の応用を考え，排水中の窒素の微生物的除去の促進について検討した．綿，レーヨンを試料として炭化実験を行い，比較的低い温度で炭化したレーヨンを固定化担体として選んだ．硝化菌を用いて微生物の付着性および窒素除去性能を検討したところ，硝化菌の固定化に対する炭化繊維の有効性が認められた．小型装置によるアンモニアモデル排水の処理実験において，炭化繊維を設置することによりアンモニア除去性能は高くなった．連続処理における固定化担体の条件を検討するために，大型矩形エアリフト気泡塔の流動特性を測定した．エネルギ収支式に基づいて液循環流量を解析し，塔内の溶存酸素濃度の分布を求めて嫌気領域の割合を推算した．炭化繊維を設置した装置としない装置を用いて連続排水処理実験を行った．BOD 除去率は同じであったが，アンモニア除去性能は炭化繊維を設置した方が高かった．

Takashi Yoshimatsu

Papers

Flow Characteristics in Cocurrent Upflow Bubble Column Dispersed with Micro-Bubbles

Influence of Micro-bubble on Ozone-Decomposition of Excess Sludge

Development of Rectangular Bubble Column for High-Grade Wastewater Treatment Using Carbonized Textile as Immobilizing Carrier