Ozone Microbubbles Research Articles

The effect of pre-treatments on atrazine removal from source water by microbubble ozonation.

Ozone-based advanced oxidation processes (AOPs) have emerged a promising avenue for water treatment, offering effective removal of micropollutants. Recent research underscores the potential of ozone microbubbles to enhance ozone mass transfer during water treatment, particularly when combined with pre-treatment steps. This study aimed to evaluate the efficacy of three different combined processes (chlorine/KMnO4/PAC pre-treatment followed by ozonation) in removing atrazine, a common micropollutant from natural source water. Results revealed that all combined processes achieved higher atrazine removal rates compared to individual pre-treatment or ozonation methods. Notably, the highest atrazine removal rates were observed under alkaline pH conditions, with treatment outcomes influenced by oxidant dose and pH levels. Among the combined processes, chlorine pre-treatment followed by ozonation emerged as the most effective approach, achieving a removal rate of 59.7% that exceeded the sum of individual treatments. However, this treatment efficacy was affected by water quality parameters, particularly the presence of organic matter and elevated ammonia nitrogen concentration (> 0.5mg/L). This study highlights the potential for utilizing ozone micro/nanobubbles to enhance ozone mass transfer and offers valuable insights for optimizing the combined application of pre-treatment and ozonation strategies for efficient atrazine removal from natural water sources.

Ozone nanobubble technology as a novel AOPs for pollutants degradation under high salinity conditions

Conventional water treatment systems frequently exhibit diminished efficiency at high salinity - a significant issue especially for real industrial effluents - mostly due to the creation of intricate structures between pollutants and salts. One of the primary obstacles associated with high salinity conditions is the generation of by-products that pose additional hurdles for treatment. In this work, we have investigated the novel advanced oxidation process a so-called ozone nanobubble technology for degradation of the pollutants at high salinity conditions. The mass transfer is often the rate-limiting step in gas-liquid process and the poor rate of mass transfer diminishes the overall efficacy. One of the primary disadvantages associated with ozone is its restricted solubility and instability when dissolved in an aqueous solution. These characteristics impose limitations on its potential applications and need the use of specialized systems to facilitate gas-liquid interaction. In this work, we have also suggested enhancing the ozonation process through the utilization of ozone nanobubbles. The findings of our experiment and subsequent analysis indicate that the presence of nanobubbles enhances the process of ozonation through three key mechanisms: (i) an increased mass transfer coefficient, (ii) a higher rate of reactive oxygen species (ROS) generation attributed to the charged interface, and (iii) the nanobubble interface serving as an active surface for chemical reactions. The predicted mass transfer coefficients were found to range from 3 to 3.5 min−1, a value that is notably greater than that seen for microbubbles. The study showcased the degradation of methylene blue dye through the utilization of ozone nanobubbles, which exhibited a much higher rate of dye degradation compared to ozone microbubbles. The confirmation of the radical degradation mechanism was achieved by the utilization of electron spin resonance (ESR) measurements. The developed process has high potential for application in industrial scale textile wastewater treatment.

Evaluating the Potential of Ozone Microbubbles for Inactivation of Tulane Virus, a Human Norovirus Surrogate

Evaluating the Potential of Ozone Microbubbles for Inactivation of Tulane Virus, a Human Norovirus Surrogate

Application of Dissolved Ozone Flotation in the Advanced Treatment of Drilling Wastewater in Gas Field: Significance of Ozone Microbubble Flocs

Application of Dissolved Ozone Flotation in the Advanced Treatment of Drilling Wastewater in Gas Field: Significance of Ozone Microbubble Flocs

THE COMPARISON OF OXIDATION EFFICIENCY OF REACTIVE OXYGEN SPECIES (ROS): PILOT SCALE OF MICROBUBBLE TECHNOLOGIES WITH OXYGEN CONCENTRATION

The objective of this study is to assess and compare the effectiveness of an oxidizing agent. Within the field of advanced oxidation processes (AOPs), ozone, a highly reactive gas, generates reactive oxygen species (ROS) as byproducts through chemical reactions. The study employed a dielectric barrier discharge (DBD) plasma generator to produce ozone gas. This study was carried out under different gas source conditions, including both air and oxygen. Additionally, the ROS produced as byproducts from the interaction between ozone gas and water were measured using oxidation-reduction potential (ORP) values. The ORP values exhibit strong foundational attributes for both ozone dissolution and ROS oxidation efficiency. To extend the interaction duration between ozone gas and water, a stone diffuser was utilized to introduce ozone gas into the water. This mechanism resulted in the creation of ozone microbubbles through a process known as cavitation. The results illustrate a positive relationship between the flow rate and ozone yield. This trend reached its highpoint with the highest observed ozone concentrations approximately 14.11 mg/L for oxygen and 4.55 mg/L for air both achieved at a flow rate of 11 L/min. Furthermore, the highest ozone concentrations were recorded at 15.17 mg/L for oxygen and 12.59 mg/L for air after a 10 min discharge period. Interestingly, ozone generated from oxygen feed gas exhibited a higher concentration yield than that from air feed gas. Moreover, the ORP value displayed a continuous increase with longer treatment times, eventually stabilizing at around the 15 min. This pattern corresponded to the water reaching its highest the ORP values approximately 821 mV for oxygen and 569 mV for air. In summary, this study emphasizes the potential benefits of utilizing ozone as an effective oxidant in both gaseous (ozone gas) and liquid (ROS) phases. It especially emphasizes the essential role played by the generation of ozone and ROS from an oxygen-fed gas source. Moreover, it highlights the significance of maintaining an optimal flow rate of 11 L/min and a discharge duration of 10 min for achieving the highest ozone concentration. Similarly, a treatment time of 15 min for the liquid phase is recommended to maximize ORP values. Both of these values indicate the highest potential advantages for producing an effective oxidant.

Mitigation of Emerging Contaminants in Hospital Wastewater: Ozone Microbubbles as an Innovative Treatment Approach

This review article explores the challenges posed by emerging contaminants present in hospital wastewater and investigates the potential of ozone microbubbles as an innovative treatment approach. As healthcare facilities continue to be a significant source of diverse contaminants, ranging from pharmaceuticals and personal care products to antibiotic-resistant bacteria, addressing the impact of these pollutants on the environment and public health is of paramount importance. The use of ozone microbubbles, a cutting-edge technology in water treatment, offers a promising solution for the removal and degradation of various emerging contaminants. This article comprehensively examines the occurrence and effects of emerging contaminants in hospital wastewater, delves into the principles of ozone microbubbles technology, and reviews recent studies and advancements in utilizing ozone microbubbles for the treatment of hospital effluents. The potential synergistic effects of combining ozone microbubbles with other treatment processes will also be explored. The aim is to provide a comprehensive overview of the current state of knowledge, identify gaps in research, and propose future directions for the effective mitigation of emerging contaminants in hospital wastewater using ozone microbubbles.

Substantial removal of four pesticide residues in three fruits with ozone microbubbles

Developing a straightforward method to remove pesticide residues from fruits is essential for food safety. In this study, ozone microbubble treatment was performed on three fruits (strawberry, cherry, and apricot) to remove four pesticide residues (emamectin benzoate, azoxystrobin, boscalid, and difenoconazole) while comparing removal efficiency. The concentration of hydroxyl radicals in different washing orientations was homogeneous at a concentration ranging between 8.9 and 10.2 μmol·L-1. Under long washing time (18 min), strawberry, cherry, and apricot obtained higher removal rates of 51 %∼65 %, 51 %∼59 % and 24 %∼70 %, respectively. Moreover, scanning electron microscopy (SEM) and contact angle (CA) revealed that apricot has better hydrophobicity, leading to a higher pesticide removal of 45 ∼ 84 % with less water and more vigorous washing. Notably, vitamin C content in fruits remain largely unchanged following ozone microbubble treatment. This study demonstrated the effectiveness of ozone microbubble treatment as pollution-free method for enhancing food safety by removing pesticide residues on fruits.

Real-time organic compound monitoring in advanced oxidation process (AOP) of anaerobic digestion effluent: introduction of UV-VIS spectrum representative index by discrete Fourier transform.

Anaerobic digestion effluent from sewage treatment plants (STP) poses a challenge to the operator because of its high organic matter and inorganic nitrogen concentrations, which require an effective process for biological treatment. This study aimed to introduce a UV-VIS spectrum representative index by discrete Fourier transform (DFT) and apply UV-Vis spectrophotometric techniques for real-time organic compound monitoring in the AOP process using anaerobic digestion tank effluent wastewater. The effect of advanced oxidation on the organic compounds of effluent using ozonation was examined. In this research, after treating secondary treated water with the UV-AOP process and anaerobic digestion effluent with ozone microbubble systems, changes in organic substances were expressed by the UV-Vis spectrum and compared with conventional water quality parameters. The anaerobic digestion process effluent was treated through ozone oxidation, had a high curve, and fell gently from 230 to 667 nm. Discrete Fourier transform (DFT) was applied to obtain representative values from the obtained spectrum. From among the coefficients obtained by analyzing the UV-Vis spectrum through DFT, an expected value was selected, and the correlation between CODMn and a3 was the highest (correlation function = 0.694, RSQ = 0.482). Therefore, a linear regression analysis was performed to determine which water quality factor it was related to.

Mineralization of Poly(vinyl alcohol) by Ozone Microbubbles under a Wide Range of pH Conditions.

Poly(vinyl alcohol) (PVA) is a well-known recalcitrant pollutant that threatens ecological systems and human health. In this study, ozone-microbubble treatment was evaluated as a physicochemical method to mineralize PVA in solution for wastewater treatment. Microbubbles are very small bubbles (<50 μm in diameter) and shrink in water because of the rapid dissolution of the interior gas. Ozone microbubbles were generated by a hybrid microbubble generator in PVA solutions with pH conditions of 2, 7, and 10. Ordinary ozone bubbling was also performed as control tests. The change in the total-organic-carbon content was measured to evaluate the efficiency of the system for wastewater treatment. Ordinary ozone bubbling was not able to mineralize aqueous PVA solutions under nonalkaline conditions, and approximately 30% of the total organic carbon remained at pH 2 and 7. Conversely, ozone microbubbles effectively mineralized PVA in aqueous solution to almost 0% in total organic carbon regardless of the pH condition. Effective mineralization of PVA, a recalcitrant organic chemical, demonstrates the potential of ozone-microbubble systems for physicochemical wastewater treatment.

Promotion effect of foam formation on the degradation of polyvinyl alcohol by ozone microbubble

Polyvinyl alcohol (PVA), extensively utilized in diverse industries, presents a challenge in terms of degradation. The combination of ozone (O3) with microbubbles enhances ozone's residence time and oxidation efficiency, offering a promising avenue for effective PVA degradation. This study investigated PVA degradation using ozone microbubble (MB/O3) and oxygen microbubble (MB/O2). Bubbles evolving into remarkably resistant foam was observed for the first time. PVA removal via MB/O3 and MB/O2 followed a first-order kinetic model, exhibiting removal rates of 98.58 % and 48.68 %, respectively, within the initial 20 min. The physicochemical reaction of PVA degradation by MB/O3 and the physical removal reaction by MB/O2 were demonstrated. The microscale changes of bubbles and foam were captured, uncovering the phenomenon of self-pressurized dissolution of MB/O3 and the creation of larger foam structures through intact microbubbles, ultimately leading to their rupture. A comprehensive four-stage theory was proposed to explain PVA degradation by MB/O3, where physical separation, foam film degradation, and bubble coalescence within the foam play crucial roles. This theory was validated under varying pH and salt concentration conditions. Moreover, when the pH was decreased from 8.69 to 3.3, there was a 33.2 % increase in the COD removal rate. Mechanism analysis further confirmed the theory and revealed that, during PVA degradation, MB/O3 underwent stochastic cleavage, yielding small molecule remnants comprising aldehyde, carboxyl, and ester moieties. Finally, by comparison with other PVA degradation processes, the trial of MB/O3 was proven to be a straightforward and effective treatment approach for PVA degradation.

Influence of ozone microbubble enhanced oxidation on mine effluent mixes and Daphnia magna toxicity

The mining industry often must mix different kinds of water on the mine site during pre-treatment or post-treatment before the final discharge of the treated water to the environment. Microbubble ozonation has proven to be efficient in the removal of contaminants of concern from mine water, such as metals, metalloids, and nitrogen compounds, which can persist in the environment and entail toxicity issues. This study evaluated the efficiency of ozone microbubbles combined with lime precipitation on contaminant removal and its impact on toxicity for Daphnia magna with five different mine effluent mixes from an active mine site located in Abitibi-Témiscamingue, QC, Canada. For the non-acidic mixes, two scenarios were tested: first, pre-treatment of metals using lime precipitation and a flocculant was conducted prior to ozonation; and second, ozonation was conducted prior to metals post-treatment using the same precipitation and flocculation technique. Results showed that the NH3–N removal efficiency ranged from 90% for the lower initial concentrations (1.1 mg/L) to more than 99% for the higher initial concentrations (58.4 mg/L). Moreover, ozonation without metals pre-treatment improved NH3–N treatment efficiency in terms of kinetics but entailed abnormal toxicity issues. Results of bioassays conducted on water with metals pre-treatment did not show any toxicity events but showed abnormal toxicity patterns on the mixes treated without metals pre-treatment (diluted effluents were toxic, while undiluted were not). At 50% dilution, the water was toxic, probably due to the potential presence of metal oxide nanoparticles. The confirmation of the source of toxicity requires further investigation.

The catalytic oxidation process of atrazine by ozone microbubbles: Bubble formation, ozone mass transfer and hydroxyl radical generation

Ozone microbubbles have received increasing attention since they can produce hydroxyl radical (•OH) to decompose ozone-resistant pollutants. Besides, compared with conventional bubbles, microbubbles have a larger specific surface area and higher mass transfer efficiency. However, the research on the micro-interface reaction mechanism of ozone microbubbles is still relatively scarce. Herein, we systematically studied the stability of microbubbles, ozone mass transfer and atrazine (ATZ) degradation through multifactor analysis. The results revealed that bubble size was dominant in the stability of microbubbles, and gas flow rate played a major role in ozone mass transfer and degradation effects. Besides, the bubble stability accounted for the different effects of pH on ozone mass transfer in two aeration systems. Finally, kinetic models were built and employed to simulate the kinetics of ATZ degradation by •OH. The results revealed that conventional bubbles could produce •OH faster compared with microbubbles under alkaline conditions. These findings shed light on the interfacial reaction mechanisms of ozone microbubbles.

Experimental Inactivation of Microalgae in Marine Ballast Water by Microbubbles Generated through Hydrodynamic Cavitation

This paper presents a novel approach to microbubble technology for the treatment of aquatic invasive organisms in ship ballast water. The microbubbles are produced by hydrodynamic cavitation with a sudden and dramatic water pressure drop. The air and ozone microbubbles, respectively, verified the bioavailability of ship ballast water treatment using marine microalgae as an indicator. Besides the effects of an ozone injection dose, the morphological changes of cells and the effluent toxicity were investigated. Compared with the ozone microbubble treatment, the inactivation of marine microalgae by air microbubbles required a long treatment time. In the storage experiment, it was found that air microbubbles did not inhibit the growth of microalgae cells, and that the injection of active matter such as ozone was still necessary to ensure the validity of biological invasion. However, even with very low doses of ozone, the inactivation effect of ozone microbubbles was still very evident. Overall, it helps to minimize the use of active matter to reduce the toxicity of treated water, and this has the capability to develop into an environmentally acceptable and practical ballast water treatment technology.

Efficiency and mechanism of ozonated microbubbles for enhancing the removal of algae and algae-derived organic matter

The effective control of eutrophication caused by algae blooms is still the focus of global attention. The traditional dissolved air floatation process for algae removal has a low adhesion efficiency between bubbles and algal cells and a low removal efficiency of organic pollutants. Aiming to address these defects, this study set up an ozone microbubble-enhanced air flotation experiment to explore the removal trends of algal cells and algal organic matter (AOM) pollution. In contrast to traditional air flotation, this approach targets the removal of various forms of AOM after algal cell damage. The highest removal rates of algal cells, extracellular microcystin (Mc), intracellular Mc-lr and total Mc-lr were 96.6%, 60.1%, 95.2% and 93.7%, respectively. Compared with the traditional process, the absorption rate and utilization rate of ozone were increased by 41.9% and 46.2%, respectively. The removal effect of AOM was also greatly improved, and ozone microbubbles enhanced the removal of aromatic protein-like substances and high-molecular-weight fulvic acid, humic acid and humic substances. The advantageous synergistic effect of ozone and microbubbles on algae removal was analyzed by exploring the enhanced air flotation removal mechanism of ozone microbubbles' enhanced air floatation removal. Good vacuole adhesion and strong oxidation caused by ozone microbubbles jointly guaranteed a good removal rate of AOM. The enhanced air flotation process with ozone microbubbles has high feasibility and a good effect, can effectively remove algal cells and algal pollutants, and has great potential in algal removal and control of water eutrophication.

Accelerated removal of five pesticide residues in three vegetables with ozone microbubbles

A simple and effective approach to remove pesticide residues on vegetables is necessary for food safety. Ozone microbubbles treatment as an eco-friendly washing technique was investigated for three vegetables (celery, pakchoi and cowpea) collected from the field applied with five pesticides. The removal rates of five pesticide residues on cowpea by ozone microbubbles treatment were 15 %–47 % higher than that by ozone macrobubbles. Moreover, compared with the other four systemic pesticides, emamectin benzoate had a preferable removal rate (65 %–94 %) as a non-systemic pesticide with high water solubility. Through Mass Spectrometry (MS), the double-bonded structure of emamectin benzoate made it more possible to be removed chemically, carrying a degradation rate of 88 % at 25 min in water. Additionally, cowpea showed low removal (28 %–65 %) owing to its stomata and rough surface with SEM. Conclusively, this study demonstrated the potential of the ozone microbubble treatment on pesticide residues removal to enhance food safety.

Removal Performance of Suspended Solid (SS) and Organic Compounds in the Pre-treatment of Actual Pharmaceutical Wastewater by Microbubble Ozonation

Actual pharmaceutical wastewater was pretreated with ozone microbubbles and compared with the treatment processes of nitrogen microbubbles, ozone common bubbles, and nitrogen common bubbles. The removal process and performance of suspended solids (SS) and organic compounds were investigated. The results showed that ozone microbubble treatment with strong adsorption-flotation-oxidation effects could enhance SS removal significantly, and the corresponding SS removal efficiency reached 81.67% at 60 min. The SS particle size was reduced, and the negative charge on the SS surface was simultaneously changed into a positive charge. Microbubble ozonation with a strong·OH oxidation effect also significantly enhanced the degradation and removal of organic compounds. The removal efficiency of soluble COD (SCOD) reached 36.60% at 60 min, and the SCOD removal was accelerated after the SS removal. The removal efficiency of UV254 also reached 36.91%. The biodegradability was improved, and the biological toxicity was obviously eliminated. The analysis of three-dimensional fluorescence and GC-MS showed that the macromolecular organic compounds with complex structure could be oxidized and decomposed efficiently with microbubble ozonation, resulting in the aromatic reduction in organic compounds in wastewater. Therefore, microbubble ozonation could be considered as an efficient and feasible pretreatment method for high concentration and refractory pharmaceutical wastewater.

Degradation of ciprofloxacin in aqueous solution using ozone microbubbles: spectroscopic, kinetics, and antibacterial analysis

Ciprofloxacin (CIP) has been listed in the last version of the surface water due to its ability to kill human cells by inhibiting the activity of DNA topoisomerase IV. Thus, CIP, along with other antibiotic pollution has become a serious threat to the environment and public health. Ozonation has been used as an advanced technique that is applied in wastewater treatment to remove CIP, but the primary limitation of this method is the low solubility of ozone in water. This study is the first report of CIP removal in a scale-up of its aqueous solution using a self-developed aerator pump-enhanced ozonation (APO) system, which only employs a propeller and a zigzag arrangement of meshes. This aerator pump decreased the size of ozone bubbles by 90% and increased the effective ozone solubility to 0.47 ppm. The mechanism of degradation of CIP is attributed to an oxidation reaction of the antibiotic with reactive oxygen species, such as hydroxyl, oxygen, and hydroperoxyl radicals, generated on the surface of the ozone microbubbles. It was found that the rate and efficiency of degradation of CIP using the APO system were 3.64 × 10−3/min and 83.5%, respectively, which is higher compared with those of conventional flow ozonation (FO) systems (1.47 × 10−3/min and 60.9%). The higher degradation efficiency of CIP by the APO system was also revealed by its higher electrical energy efficiency (0.146 g/kWh), compared to that of the FO system (0.106 g/kWh). The degradation of CIP was also monitored by the resulting antibacterial activity against Escherichia coli and Staphylococcus aureus.

Interaction Mechanisms and Application of Ozone Micro/Nanobubbles and Nanoparticles: A Review and Perspective.

Ozone micro/nanobubbles with catalytic processes are widely used in the treatment of refractory organic wastewater. Micro/nanobubble technology overcomes the limitations of ozone mass transfer and ozone utilization in the application of ozone oxidation, and effectively improves the oxidation efficiency of ozone. The presence of micro/nanobubbles keeps the catalyst particles in a dynamic discrete state, which effectively increases the contact frequency between the catalyst and refractory organic matter and greatly improves the mineralization efficiency of refractory organic matter. This paper expounds on the characteristics and advantages of micro/nanobubble technology and summarizes the synergistic mechanism of microbubble nanoparticles and the mechanism of catalyst ozone micro/nanobubble systems in the treatment of refractory organics. An interaction mechanism of nanoparticles and ozone microbubbles is suggested, and the proposed theories on ozone microbubble systems are discussed with suggestions for future studies on systems of nanoparticles and ozone microbubbles.

Antibacterial Efficacy and Physiochemical Effects of Ozone Microbubble Water on Tomato

The consumption of fresh produce is steadily increasing and chlorine washing is the most commonly used method of disinfecting fresh produce. However, chlorine washing possesses a potential risk. Hence, this study used ozone microbubble (OMB) water to disinfect Salmonella Enteritidis, S. Typhimurium, Staphylococcus aureus, and Escherichia coli on tomatoes. After injecting ozone into the microbubble generator, OMB was fulfilled in a 10 L tank for 10 or 20 min. The inoculated tomatoes were washed for 30 or 60 s. Control groups included unwashed, water-washed, microbubble-only, and ozone-only. The microbial populations were significantly lower on the OMB-treated tomatoes than controls (p &lt; 0.05), but not between various fulfilling or treatment time (p &gt; 0.05). When tomatoes were treated with OMB with 10 min fulfilling and 30-s washing, the differences of tested bacteria and water washing, ozone-only, and microbubble-only were: S. Enteritidis: 4.11, 3.37, 2.54 log CFU/tomato; S. Typhimurium: 4.83, 4.50, 2.78 log CFU/tomato; E. coli: 4.31, 4.08, 2.09 log CFU/tomato; S. aureus: 4.12, 3.93, 2.82 log CFU/tomato. In addition, significant higher ozone concentrations and conductivity were detected in OMB water than other groups (p &lt; 0.05). Color, texture, and sensory characteristics of the OMB-treated tomatoes were not significantly different from other groups (p &gt; 0.05). This study demonstrated that OMB effectively inactivated bacteria on tomatoes and did not affect the physical and sensory characteristics of tomatoes.

Oxidation of bisphenol-A by ozone microbubbles: Effects of operational parameters and kinetics study

The removal of bisphenol-A (BPA) from aqueous medium by ozone microbubbles (OMBs) was studied in this work. The removal efficiency of BPA was improved from 41 to 98% within 600 s of ozonation when the initial pH of the medium was increased from 3 to 7. The stoichiometric ratio of the moles of ozone consumed to the moles of BPA removed was found to be in the range of 0.228–0.276 at pH 7 and 0.125 mol m − 3 initial concentration of BPA. A considerably high range of ozone utilization efficiency (i.e., 52%–86%) for the complete removal of BPA was achieved by using the OMBs. Based on the TOC removal, three stages of ozonation (i.e., 0–0.6, 0.6–2.5, and 2.5–3.0 ks) were observed. Their corresponding (observed) reaction rate constants were 294.1, 1365.3, and 2477.7 dm 3 mol − 1 s − 1 , respectively. The oxidation of BPA by ozone followed a first-order kinetics with respect to both BPA and ozone, and an overall second-order kinetics. The Hatta number was low (i.e., 0.01–0.054), which proves that the mass transfer resistance was negligible, implying that the rate of mass transfer was enhanced by the OMBs. • OMBs were very efficient for the oxidation and mineralization of BPA. • Oxidation of BPA was achieved both by the direct and indirect reactions with ozone. • A high range of ozone utilization efficiency was achieved by the OMBs. • Based on the TOC removal, three stages of ozonation were observed. • The low Hatta number proved that the mass transfer resistance was negligible.