Porous Venturi-Orifice Microbubble Generator for Oxygen Dissolution in Water

Abstract

Microbubbles with slow rising speed, higher specific area and greater oxygen dissolution are desired to enhance gas/liquid mass transfer rate. Such attributes are very important to tackle challenges on the low efficiency of gas/liquid mass transfer that occurs in aerobic wastewater treatment systems or in the aquaculture industries. Many reports focus on the formation mechanisms of the microbubbles, but with less emphasis on the system optimization and assessment of the aeration efficiency. This work assesses the performance and evaluates the aeration efficiency of a porous venturi-orifice microbubble generator (MBG). The increment of stream velocity along the venturi pathway and orifice ring leads to a pressure drop (Patm > Pabs) and subsequently to increased cavitation. The experiments were run under three conditions: various liquid velocity (QL) of 2.35–2.60 m/s at fixed gas velocity (Qg) of 3 L/min; various Qg of 1–5 L/min at fixed QL of 2.46 m/s; and free flowing air at variable QLs. Results show that increasing liquid velocities from 2.35 to 2.60 m/s imposes higher vacuum pressure of 0.84 to 2.27 kPa. They correspond to free-flowing air at rates of 3.2–5.6 L/min. When the system was tested at constant air velocity of 3 L/min and under variable liquid velocities, the oxygen dissolution rate peaks at liquid velocity of 2.46 m/s, which also provides the highest volumetric mass transfer coefficient (KLa) of 0.041 min−1 and the highest aeration efficiency of 0.287 kgO2/kWh. Under free-flowing air, the impact of QL is significant at a range of 2.35 to 2.46 m/s until reaching a plateau KLa value of 0.0416 min−1. The pattern of the KLa trend is mirrored by the aeration efficiency that reached the maximum value of 0.424 kgO2/kWh. The findings on the aeration efficiency reveals that the venturi-orifice MBG can be further optimized by focusing on the trade-off between air bubble size and the air volumetric velocity to balance between the amount of available oxygen to be transferred and the rate of the oxygen transfer.

Micro-nano bubbles assisted laccase for biocatalytic degradation of bisphenols

“…Oxygen is the substrate of Lac, and it is reduced directly to water by a four-electron mediator-less mechanism with concomitant one electron oxidation of an organic substrate like BPA [53]. Increases in air intake lead to higher oxygen dissolution until it reaches saturation [54]. However, the overflowing air into the system might not contribute to the dissolved oxygen concentration if the time for oxygen dissolved in the water is too short or the bubble size is too large.…”

Smart Aero-Spider: An adaptive and selective smart switching aerator system

“…Spider Aerator The output of the splitter is connected to the respective spider aerator which is capable of producing microbubbles [12] which help in uniform aeration and does not interfere with the aquatic life. Figure 11 demonstrates how a spider aerator works by the author.…”

Effect of Power Pump and Nozzle Diameter Microbubble Generator to Increase Oxygen Concentration in Aquaculture

“…One alternative application is high-performance aerators with microbubble technology. This technology is better known as microbubble generators (MBG or MBGs) (Afisnaa et al, 2017;Alfarraj et al, 2020;Basso et al, 2018;Juwana et al, 2019;Liew et al, 2020). MBG can produce micro-sized bubbles (Deendarlianto et al, 2015;Rizaldi et al, 2019) and accelerate to increase DO concentration (Jeon et al, 2018;Rahmawati et al, 2021), and save energy (Parmar & Majumder, 2013).…”

“…MBG can produce micro-sized bubbles (Deendarlianto et al, 2015;Rizaldi et al, 2019) and accelerate to increase DO concentration (Jeon et al, 2018;Rahmawati et al, 2021), and save energy (Parmar & Majumder, 2013). There are various methods for generating a microbubble technology: Using venturi (Dey et al, 2020;Huang et al, 2021;Wilson et al, 2021;Yadav et al, 2019), using Nozzle (Alam et al, 2018;Ferrando et al, 2021;Khan et al, 2020;Kim & Lee, 2021;Lee et al, 2019;Lin et al, 2018;Wu et al, 2021), using Orifice (Basso et al, 2018;Daskiran et al, 2019;Deendarlianto et al, 2015;Juwana et al, 2019;Kataoka et al, 2020;Liew et al, 2020;Miao et al, 2021;Morito & Makuta, 2018;Rizaldi et al, 2019;Sadatomi et al, 2012), and used DAF Kiuru, 2001). However, various microbubbles have a reasonably small dimension size, and some use compressors or blowers for air distribution.…”