Microbubble Aeration Research Articles

Dielectric barrier discharge plasma in-situ microbubble aeration with peroxymonosulfate for levofloxacin degradation: Microbubble superior performance and pH-dependent mechanism

In this study, a simple ceramic membrane aeration was used to realize dielectric barrier discharge/peroxymonosulfate (DBD/PMS) in-situ microbubble aeration for effective dispersion and gas–liquid transfer of highly active substances. Compared with conventional aeration, ceramic membrane aeration had 18 times fewer microbubble diameters (110–180 µm), much higher bubble densities, and 1.6–2.1 times higher aquatic O3 concentrations at pH 4.8–10.0. Consequently, the yield of HO and SO4·- was 1.64–2.34 and 1.13–2.93 times, respectively, via faster O3 transfer to the aquatic solution and enhanced PMS activation. DBD/PMS microbubble aeration outperformed conventional aeration, with a 2.52-fold increase in LEV degradation kinetics and a 2.79-fold increase in TOC removal. Quenching and EPR experiments showed that HO and 1O2 were the main reactive oxygen species (ROS) for LEV degradation. The yield of O2·- was higher at pH 6.9, while HO, SO4·-, and 1O2 was higher at pH 8.7 derived from a series of complex reactions. The LEV degradation pathway was pH-dependent, with the HO-oxidation contribution varying from 25.3% to 44.3% as the pH increased from 4.8 to 8.7, while other ROS (1O2 and O2·-)-oxidation decreased from 73.1% to 51.8%. Therefore, this work will advance the current understanding of the intrinsic effects of pH in the plasma/PMS microbubble process for wastewater purification.

A Novel Coupling of a Biological Aerated Filter with Al3+ Addition-O3/H2O2 with Microbubble for the Advanced Treatment of Proprietary Chinese Medicine Secondary Effluent

The advanced treatment of proprietary Chinese medicine secondary effluent (PCMSE) was strongly needed with the recent implementation of a more stringent discharge standard. Based on the features of PCMSE and the reuse of Al3+from wastewater from soaking of Pinellia Ternata with alumen (WSPTA), three new combined processes were designed for the advanced treatment of PCMSE on a larger pilot scale. A pilot scale study showed that compared with two other combined processes, the new coupling of a biological-aerated filter with Al3+ addition (BAFA)-O3/H2O2 with microbubble (OHOMB) (CBAFAOHOMB) obtained the maximum pollutant removal (with removals of 91.71%, 94.64%, and 82.32% being observed for color, total phosphorus (TP), and chemical oxygen demand (COD), respectively) and acquired the lowest Al3+residual in the effluent. During CBAFAOHOMB treatment of PCMSE, the vast majority of TP elimination, 35.20% of COD removal, and 49.40% of color removal were achieved by BAFA; OHOMB obtained 64.80% of COD removal and 60.60% of color removal, and biofilm activity in BAFA slightly changed under a 10 mg/L Al3+ dose. Furthermore, microbubble aeration was more efficient in removing organics than conventional bubble aeration during O3/H2O2 oxidation, and suspended solid (SS) relatively significantly lowered oxidation ability in the OHOMB system. These results indicated that CBAFAOHOMB markedly integrated advantages of BAFA and OHOMB, and was a proposed process for the advanced treatment of PCMSE. Meanwhile, it was feasible that WSPTA was reused for PCMSE treatment as an Al3+ source.

Impacts of micron-sized aeration bubble on sludge properties and hydraulic dynamics in relation to membrane fouling alleviation

This investigation elucidates the influence of micron-scale aeration bubbles on the improvement of anti-fouling characteristics within submerged membrane bioreactors (sMBRs). A systematic examination of sludge properties, hydraulic dynamics, and fouling tendencies revealed that the application of microbubble aeration, specifically at dimensions of 100 μm, 80 μm, and 30 μm, significantly reduced sludge electrostatic repulsion and augmented particle size distribution, as opposed to the utilization of coarse bubble aeration of 1 mm. Notably, the employment of 100 μm bubbles achieved a significant reduction in the proportion of smaller particles (<10 μm) and sludge viscosity, thereby facilitating a more homogenous and vigorous turbulence at the membrane interface. These optimized conditions were instrumental in the substantial reduction of membrane fouling, which was corroborated by the diminished rate of fouling, reduced resistance accumulation, and lesser foulant deposition. The investigation identified sludge particle size, turbulent kinetic energy, and shear stress as the predominant factors influencing the development of membrane fouling. The findings underscore the pronounced advantages of employing 100 μm-sized bubbles in aeration strategies, providing enhanced understanding for the optimization of aeration parameters to improve sMBR efficiency and maintenance.

Reusing biofloc-culture water and microbubble aeration for culturing the white-leg shrimp Litopenaeus vannamei

This study investigated the effects of reusing biofloc-culture water for culturing the white-leg shrimp Litopenaeus vannamei. Experiments were conducted for two continuous cycles without water exchange for 30 days during the nursery stage. The studies were performed with two different aeration systems, namely microbubbles (MB) and large air bubbles (LB). Water quality parameters such as dissolved oxygen (DO), temperature, pH, salinity, alkalinity, total ammonia nitrogen (TAN), nitrite, nitrate, settleable solids (SS), and total suspended solids (TSS) were recorded throughout the culture days. Also, comparisons were performed on parameters of the shrimp growth, i.e., body weight and length, feed conversion ratio (FCR), and specific growth rates (SGR) for the 30-day culture for Cycles 1 and 2. Cycle 2 showed no deterioration in water quality and no significant difference in growth performance compared to Cycle 1 for either aeration method (MB and LB). However, when comparing between aeration methods, MB aeration significantly improved the DO of the water and accelerated the conversion of TAN to nitrate. Shrimps in the MB aeration system were significantly larger (by 39%) with a lower FCR value (reduced by 30%) than in the LB aeration system. Harmful bacteria from the Vibro group were detected. However, they occurred at a minimum level in both cycles and aeration types. Overall, the biofloc-culture water might be reused for the subsequent cycle, while the MB aeration might promote the growth of biofloc and L. vannamei.

Integration of seeding-induced crystallization with microbubble aeration for membrane fouling and wetting control in vacuum membrane distillation

In this work, a bench-scale vacuum membrane distillation crystallization (VMDC) system coupled with microbubble aeration (MBA) was developed for treating high-salinity feed brine. Herein, the effect of seeding dose on membrane fouling and wetting control in the VMDC system was studied by using synthetic saturated calcium sulfate solution. The results showed that introducing gypsum seeds at a dose of 0.5 g/L effectively restricted membrane fouling and wetting. Subsequently, seeding-induced crystallization coupled with MBA was employed to investigate the control effect on membrane fouling and wetting during VMDC with simulated high-salinity feed brine treatment. As 0.5 g/L gypsum seeds were directly added at 7 h in the VMDC experiment while employing MBA, membrane fouling and wetting were effectively controlled. Finally, the mechanism behind the control of membrane fouling and wetting was elucidated during VMDC operation by integrating seeding-induced crystallization with MBA. This could be ascribed to the synergic effect of gypsum seeds and microbubbles in bulk solution. In brief, this work offers a promising approach to control membrane fouling and wetting during concentrating high-salinity wastewater by VMD.

Industrial wastewater treatment using venture injector type Micro-bubble aeration as a reduction of dissolved Iron (Fe2+) levels

Water quality problems that are often encountered, especially by-product wastewater resulting from industrial processes that do not meet the requirements for wastewater quality standards. Iron levels in wastewater can cause the water to turn brownish yellow and produce an unpleasant odor, which of course has a big impact on the environment. Therefore, it is necessary to implement a treatment process to reduce the iron level in the water, ensuring that the water is safe when discharged into the environment. The purpose of this research is to analyze the initial parameters of temperature, pH, TDS, TSS, dissolved oxygen (DO) and dissolved iron (Fe2+) in industrial waste water and then wanted to know whether the venture injector type micro bubble aeration process was able to increase the value of dissolved oxygen (DO) and decrease the dissolved iron content (Fe2+) in wastewater and to know the micro bubble type aeration process Venture injectors are the best to use. The research was conducted with an experimental design using a completely randomized design (RAL) with two factors: air flow (2 LPM, 4 LPM, and 6 LPM) and aeration time (0 minutes, 15 minutes, 30 minutes, 45 minutes, and 60 minutes), each with two repetitions. In the results of the initial parameter analysis, the pH value was 8.02 (alkaline), the temperature value was 28°C, the TDS value was 1548.3 mg/L, the TSS value was 291 mg/L, the DO value was 0.1 mg/L and dissolved iron (Fe2+) of 7.453 mg/L. After conducting research, it was found that the venture injector type micro bubble aeration process was able to increase the value of dissolved oxygen (DO) and reduce dissolved iron (Fe2+) in industrial waste water, the best increase in dissolved oxygen (DO) at 6 LPM air flow for 60 minutes was able to increase oxygen dissolved (DO) to 2.40 mg/L. The most efficient and effective reduction in the value of dissolved iron (Fe2+) at 6 LPM air flow with a time of 15 minutes was able to reduce the value of dissolved iron by 84.42%.

Effects of micro-bubble aeration on the pollutant removal and energy-efficient process in a floc–granule sludge coexistence system

Abstract To investigate energy-saving approaches in wastewater treatment plants and decrease aeration energy consumption, this study successfully established a floc–granule coexistence system in a sequencing batch airlift reactor (SBAR) employing micro-bubble aeration. The analysis focused on granule formation and pollutant removal under various aeration intensities, and compared its performance with a traditional floc-based coarse-bubble aeration system. The results showed that granulation efficiency was positively associated with aeration intensity, which enhanced the secretion of extracellular polymeric substances (EPSs) and facilitated granule formation. The SBAR with the micro-aeration intensity of 30 mL·min−1 showed the best granulation performance (granulation efficiency 52.6%). In contrast to the floc-based system, the floc–granule coexistence system showed better treatment performance, and the best removal efficiencies of NH4+-N, TN, and TP were 100.0, 77.0, and 89.5%, respectively. The floc–granule coexistence system also enriched higher abundance of nutrients removal microbial species, such as Nitrosomonas (0.05–0.14%), Nitrospira (0.14–2.32%), Azoarcus (2.95–12.17%), Thauera (0.43–1.95%), and Paracoccus (0.76–2.89%). The energy-saving potential was evaluated, which indicated it is feasible for the micro-aeration floc–granule coexistence system to decrease the aeration consumption by 14.4% as well as improve the effluent.

Microbubble Oxidation for Fe2+ Removal from Hydrochloric Acid Laterite Ore Leachate.

After the atmospheric hydrochloric acid leaching method is used to treat laterite ore and initially purify it, the extract that results often contains a significant amount of Fe2+ impurities. A novel metallurgical process has been proposed that utilizes microbubble aeration to oxidize Fe2+ ions in laterite hydrochloric acid lixivium, facilitating subsequent separation and capitalizing on the benefits of microbubble technology, including its expansive specific surface area, negatively charged surface attributes, prolonged stagnation duration, and its capacity to produce active oxygen. The study examined the impacts of aeration aperture, stirring speed, oxygen flow rate, pH value, and reaction temperature. Under optimized experimental conditions, which included an aeration aperture of 0.45 µm, stirring at 500 rpm, a bubbling flow rate of 0.4 L/min, pH level maintained at 3.5, and a temperature range of 75-85 °C, the oxidation efficiency of Fe2+ surpassed 99%. An analysis of the mass transfer process revealed that microbubble aeration markedly enhances the oxygen mass transfer coefficient, measured at 0.051 s-1. The study also confirmed the self-catalytic properties of Fe2+ oxidation and conducted kinetic studies to determine an apparent activation energy of 399 kJ/mol. At pH values below 3.5, the reaction is solely governed by chemical reactions; however, at higher pH values (>3.5), both chemical reactions and oxygen dissolution jointly control the reaction.

Modification of the distribution of humic acid complexations by introducing microbubbles to membrane distillation process for effective membrane fouling alleviation

Membrane fouling caused by inorganic ions and natural organic matters (NOMs) has been a severe issue in membrane distillation. Microbubble aeration (MB) is a promising technology to control membrane fouling. In this study, MB aeration was introduced to alleviate humic acid (HA) composited fouling during the treatment of simulative reverse osmosis concentrate (ROC) by vacuum membrane distillation (VMD). The objective of this work was to explore the HA fouling inhibiting effect by MB aeration and discuss its mechanism from the interfacial point of view. The results showed that VMD was effective for treating ROC, followed by a severe membrane fouling aggravated with the addition of 100 mg/L HA in feed solution, resulting in 45.7% decline of membrane flux. Analysis using the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory and zeta potential distribution of charged particles proved the coexistence of HA and inorganic cations (especially Ca2+), resulting in more serious membrane fouling. The introduction of MB aeration exhibited excellent alleviating effect on HA-inorganic salt fouling, with the normalized flux increased from 19.7% to 37.0%. The interfacial properties of MBs played an important role, which altered the zeta potential distributions of charged particles in HA solution, indicating that MBs adhere the HA complexations. Furthermore, this mitigating effect was limited at high inorganic cations concentration. Overall, MBs could change the potential characteristics of HA complexes, which also be used for other similar membrane fouling alleviation.

Experimental measurements on the microbubble characteristics and dissolved oxygen (DO) in water using single and twin-Venturi type microbubble generators

The aim of this paper is to develop low cost and low power consumption microbubble generator to improve the mass transfer of gas to liquid. Microbubble aeration used in aquaculture to improve dissolve oxygen level, water recycling through dissolved air flotation (DAF), oil refinement and reduction of skin friction on ship Hull. A single Venturi and 3 twin-Venturis microbubble generators are manufactured and tested in this study. Experimental data on microbubbles diameters distribution and dissolved oxygen are presented. The main conclusions are: i) the mean microbubbles diameters produced by twin-Venturi are smaller by 10 µm than single Venturi generator; ii) the dissolved oxygen concentration was higher for twin-Venturi microbubble generator; iii) the microbubbles size distribution from twin-Venturis have a narrower distribution which reduces the probability of bubbles coalesce as they have very close values of velocities; iv) the bubbles diameters and velocities increase with the height in the water tank.

Treatment of high-salinity brine containing dissolved organic matters by vacuum membrane distillation: A fouling mitigation approach via microbubble aeration

In this study, a laboratory-scale vacuum membrane distillation (VMD) system coupled with microbubble aeration (MBA) was developed for the treatment of high-salinity brine containing organic matters. Herein, at the beginning, feedwater only containing model organics such as humic acid (HA), bovine serum albumin (BSA) and sodium alginate (SA) was utilized to investigate the organic-fouling behavior, results indicated that the permeate flux was not affected by a thin and loose contaminated layer deposited on the membrane surface. Furthermore, dissolved organics in the feed brine inhibited the occurrence of membrane wetting due to the existence of a compact and protective crystals/organic-fouling layer, which can prevent the intrusion of scaling ions into membrane substrates. Besides, organics in the feedwater have a high tendency to adsorb on the membrane surface based on molecular dynamics simulations, thus, forming an organic-fouling layer prior to inorganic scaling. Finally, the effect of MBA on fouling alleviation was evaluated in VMD system, nearly 50% of salt precipitation from fouled membrane was effectively removed with the introduction of MBA, which can be ascribed to a combination of mechanisms, including surface shear forces and electrostatic attractions induced by microbubbles, meanwhile, about 2.2% of the total energy was only consumed, when using MBA. Together, these results demonstrated that MBA was a promising approach to alleviate membrane fouling in VMD.

Ozone micro-bubble aeration using the ceramic ultrafiltration membrane with superior oxidation performance for 2, 4-D elimination

Micro-bubble aeration is an efficient way to promote ozonation performance, but the technology is challenged by extensive energy cost. Here, a ceramic ultrafiltration membrane was used to achieve ozone micro-bubble (0–80 µm) aeration in a simple way at gaseous pressures of 0.14–0.19 MPa. Compared with milli-bubble aeration, micro-bubble aeration increased the equilibrium aquatic O3 concentrations by 1.53–3.25 times and apparent O3 transfer rates by 3.12–3.35 times at pH 5.0–8.0. Consequently, the •OH yield was 2.67–3.54 times via faster O3 transfer to the aquatic solution followed by decomposition rather than interfacial reaction. Ozone micro-bubble aeration outperformed milli-bubble aeration, with the degradation kinetics of 2,4-D being 3.08–4.36 times higher. Both O3-oxidation and •OH oxidation were important to the promotion with the contributions being 35.8%-45.9% and 54.1%-64.2%, respectively. The operational and water matric conditions influenced the oxidation performance via both O3 oxidation and •OH oxidation, which is reported for the first time. In general, the ceramic membrane offered a low-energy approach of ozone micro-bubble aeration for efficient pollutant degradation. The O3 oxidation and •OH oxidation were proportionally promoted by ozone micro-bubble due to O3 transfer enhancement. Thus, the promotive mechanism can be interpreted as the synchronous enchantment on ozone exposure and •OH exposure for the first time.

Janus ceramic membranes with asymmetric wettability for high-efficient microbubble aeration

Microbubbles have drawn increasing attention due to their wide applications in many fileds such as energy production, environmental remediation, and chemical and petrochemical industries. How to facilely and efficiently produce microbubbles is still keeps a great challenge. Herein, we report a Janus ceramic membrane with asymmetric wettability for high-efficient microbubble aeration. The pristine hydrophilic ceramic membrane was firstly modified by 1H,1H,2H,2H-perfluorooctyltrimethoxysilane (PFTMS), and then functionalized through single-surface deposition of polydopamine (PDA) to achieve a Janus ceramic membrane with asymmetric surface wettability. Results highlight that the introduction of DA with suitable concentration and modification time is highly efficient for the control of surface wettability. Compared to the pristine and hydrophobic modified ceramic membranes, the use of the Janus ceramic membrane allows a uniform microbubble-in-liquid dispersion system at relatively low transmembrane pressure, and as a result, the dissolved oxygen concentration is effectively increased by 1.3 times. The bubble size is stable at about 160 μm in a 24 h continuous run, and the Janus ceramic membrane shows excellent stability. Our study demonstrates the effectiveness of fabricating Janus ceramic membranes and the advantages of Janus ceramic membranes in microbubble aeration.

Enhancing the performance of alkali-activated material based coral concrete through microbubble aeration clean technology

The porous nature of coral aggregate challenges the manufacturing of high performance coral concrete, which obstacles its development and application. By using microbubble aeration clean technology, this study reports an ecofriendly and economical method to modify coral aggregates. This improvement can overcome the technical bottleneck of manufacturing high performance coral concrete. Innovatively, phosphoric acid (which is also a retarder) was used to clean the original coral aggregate particles, and alkali-activated materials (AAMs) were used to coat coral aggregates. Subsequently, AAMs were used as binder to manufacture the high performance coral concrete. The microbubble aeration cleaning removed loose attachments and soft layer on the surface of coral aggregates. It improved the filling effect of AAM coating into pores and enhanced the interfacial bonding between the aggregate and the AAM coating. The microbubble aeration clean technology modified the interfacial transition zone of coral concrete, successfully solved the problem of poor interface between coral aggregates and mortar. The residual phosphoric acid and phosphate on the aggregates could prolong the setting time of AAM based coral concrete. Comparing to the concrete prepared with original coral aggregates, the concrete prepared using the proposed new method extended initial and final setting times by 34 min and 54 min, improved flexural strength by 32.9% and compressive strength by 35.1%, meeting the performance requirements of the most ocean reef construction requirements.

Enhanced enzyme stability and gas utilization by microbubble aeration applying microporous aerators

One of the key elements in stirred tank reactor set-ups is the submersed aeration system. Aeration with microbubbles provides high gas utility coupled with prolonged enzyme stability by lowering the interfacial area renewing rate depending on the aeration mode.

Degradation of dibutyl phthalate by ozonation in the ultrasonic cavitation-rotational flow interaction coupled-field: performance and mechanism.

Dibutyl phthalate (DBP) is present in hydraulic fracturing flowback and produced water. Degradation of DBP in aqueous by means of ozonation in ultrasonic cavitation-rotational flow interaction coupled-field (UC-RF coupled-field) was studied. The effect of ozone dosage, ozone intake flow, operating temperature, initial pH, DBP initial concentration, liquid flow rate, and ultrasonic power on the DBP removal was investigated. Results indicated that the DBP degradation rate was strongly influenced by the liquid flow rate and the ultrasonic power over the range investigated. HCO3- and Cl- revealed an inhibitory effect on the DBP removal. SO42- seemed to have no effect on DBP removal. The ozone utilization efficiencies in the UC-RF coupled-field were 2.77 and 1.13 times higher than those in the conventional microporous aeration (CMA) and rotating-flow microbubble aeration (RFMA), respectively. The DBP degradation rate was diminished in the presence of tert-butyl alcohol. Cavitation bubbles are considered as innumerable microreactors. Degradation of DBP by direct ozonation, hydroxyl radical (·OH) oxidation, high pressure, and high-temperature pyrolysis was demonstrated. Finally, a possible degradation pathway of DBP is obtained on the basis of the main reaction intermediates.

Microbubble Aeration in A Recirculating Aquaculture System (RAS) Increased Dissolved Oxygen, Fish Culture Performance, and Stress Resistance of Red Tilapia (Oreochromis sp.)

Microbubble aeration has been recognized as a tool to improve dissolved oxygen and fish culture performance in limited water aquaculture. This research aims to investigate the effect of microbubble aeration on increasing dissolved oxygen, fish culture performance, and stress resistance of red tilapia. The study used 3 treatments of aerations namely microbubble, blower, and without aeration with 3 replicates each. Red tilapia weighing 115.27±3.93 g were stocked in a plastic tank of 800 L water volume at density 50 individual/tank and cultured for 50 days in a recirculating aquaculture system (RAS). Dissolved oxygen, fish culture performance, and stress resistance were evaluated. Dissolved oxygen was monitored daily. In the middle of the research period, a stress test was performed using different salinity at 12 and 24 ppt. Statistical analysis was subjected to water quality, fish culture performance, and stressed resistance. The microbubble aeration was able to stabilize DO level on 4.28 mg/L until the end of the experiment and suppressed the CO2 and ammonia content. Fish biomass was higher in microbubble treatment, with a lower FCR value, lower stress level indicating fish in good health and promoting good culture performance.&#x0D; HIGHLIGHTS&#x0D; &#x0D; The critical parameter of water quality in aquaculture is dissolved oxygen (DO) and to increase its content is by aeration&#x0D; A nobel microbubble aeration was able to increase DO level higher than blower aeration and stabilize DO at requirement level until the end of the fish culture&#x0D; The strong relationship of DO with fish hematology parameters those more stable that indicate a lower stress level&#x0D; Stable physiological conditions and low stress of fish implied that the cultivated fish is in good health and good performance by microbubble aeration&#x0D; &#x0D; GRAPHICAL ABSTRACT

Design and experimental evaluation of a Venturi and Venturi-Vortex microbubble aeration system

This work presents an experimental evaluation of a Venturi and Venturi-Vortex microbubble aeration system, taking as input variables the water-air flow ratio, water renewal time and area-volume ratio of the water tank. The aeration process response variables are defined in terms of oxygen transfer and aeration efficiency through the standard volumetric mass transfer coefficient (KLa20), standard oxygen transfer rate (SOTR), and standard aeration efficiency (SAE). Two methods of air injection were analyzed: 1. Air injection in the throat chamber of the Venturi generator; 2. air supplying in the suction side of the hydraulic pump of the aeration system. Experimental results indicate that the water renewal time variable (RT) is a statistically significant factor with respect to the KLa20, which can be maximized by decreasing RT. The effects of the variable flow ratio (FR) are greater than the effects of renewal time and area-volume ratio (AVR) concerning SOTR and SAE, indicating a maximum response with a minimum flow ratio, using the Venturi-Vortex microbubble generator. When the flow ratio decreases, the air flow increases, generating and transferring a greater amount of microbubbles (MB) into the water. It was found that increasing the air flow produced an increase in the standard oxygen transfer rate SOTR and standard aeration efficiency SAE. Results allow concluding that the injection of the air flow from the suction side of the pump promotes the generation of microbubbles (MB) for a maximum air flow allowed by the system. SOTR and SAE could be maximized whit the flow ratio factor and the Venturi-Vortex generator, supplying air flow from the suction side of the hydraulic pump.

Use of microbubble generator on the growth vannamei shrimp culture

The advanced challenges from the vannamei shrimp cultivation nowadays keep on pushing the fisheries industry on improving its productivity, however, with minimum use of water resource and an efficient land. This research aims to discover the growth and survival rate of vannamei shrimp that is cultivated in a circular tarpaulin pond with a microbubble aeration system. This research shows that microbubble can increase the amount of dissolved oxygen (DO) within the tarpaulin pond, in which the value of DO in the system blower is 3.69 Mg/L and 5.05 Mg/L in the microbubble system. The DO value within the tarpaulin pond with the microbubble system also affects the growth and viability of the shrimp, in which the growth of shrimp cultivated in the microbubble tarpaulin pond is greater (10.16 gr) than those cultivated in the blower pond (8.77 gr). Moreover, microbubble is more efficient on the use of shrimp’s feed provided with the smaller FCR value than the blower group. The application of microbubble in the circular tarpaulin pond with a high density of population can increase the amount of dissolved oxygen and therefore support the growth of aerobic bacteria to prevent air quality degradation in consequence to increase the viability of the shrimp.

Vacuum membrane distillation for seawater concentrate treatment coupled with microbubble aeration cleaning to alleviate membrane fouling

In this study, a laboratory-scale vacuum membrane distillation (VMD) system was applied to treat seawater concentrate using a hydrophobic polytetrafluoroethylene (PTFE) membrane with an effective area of 120 cm2. At the beginning, the VMD performance was investigated under different temperature and vacuum pressure. Results indicated that running temperature and vacuum pressure were optimal at 65 °C, 0.09 MPa, respectively in order to obtain an appropriate permeate water flux. Furthermore, four types of synthetic seawater concentrate with different ionic compositions, namely, SW-1, SW-2, SW-3, SW-4, was used as feed solutions for studying the VMD performance at 65 °C, 0.09 MPa. Results confirmed that the existence or absence of scaling ions would observably affect the VMD performances. For instance, concentration factor in the SW-4 test without scaling ions can reach 3.99 (i.e., 20.09 wt%), compared to the SW-1 test. Besides, we briefly elucidate the whole fouling behavior in VMD, the reason is that scaling ions could easily generate sediment substances on the surface or in the pores of membranes. In view of appearance of membrane fouling, finally, unlike conventional membrane cleaning methods, microbubble aeration (MBA) cleaning as a green approach, without chemicals consumed during cleaning, was proposed to alleviate membrane fouling, meanwhile, the mechanism of performance enhancement by MBA cleaning was also illustrated, with the introduction of microbubbles (MBs), a gas-liquid two-phase flow could intensify the surface shear and adhesion effects near the membrane surface, and also generate an electrostatic repulsion effect between membrane surface and MBs. Together, these results show that MBA cleaning is an effective method to mitigate membrane fouling in VMD.