Ozone Mass Flow Research Articles

Inactivation of waterborne Klebsiella pneumoniae with ozone to diminish the risk of hospital effluents using an absorption-based process

In this work, the inactivation of the waterborne antibiotic-resistance bacteria (ARB) Klebsiella pneumoniae (K. pneumoniae) has been evaluated to reduce the health risk in hospital environments by using an absorption process employing an ozone gas stream generated by commercially available electro-ozonizers (MIKROZON® cell). The ozone mass flow generated in the gas stream ranges from 0.026 to 0.047 mg min−1 depending on the applied intensity (0.1, 0.25, or 0.5 A). The results show that the disinfection rate improves as the mass flow of ozone gas increases and is significantly influenced by the organic matter content of the target liquid solutions. Specifically, log reductions of 1, 4, and 6 were achieved at the end of the 180-min treatment of hospital urine when intensities of 0.1, 0.25, and 0.5 A were applied, respectively. In addition, the logarithmic removal of four Antibiotic Resistance Genes (ARGs) was investigated to control the spread of antibiotic resistance through horizontal transfer processes. Logarithmic removals of 5.43, 3.17, 3.04, and 2.89 were obtained for aac(6′)-Ib, blaTEM, blaSHV, and blaKPC, respectively, during the treatment of urine (0.047 mg min−1 of ozone gas). A comprehensive comparison of the removal of these four ARGs with other disinfection technologies is also provided. It can be concluded that this work presents promising results that have the potential to increase the technology readiness level of the MIKROZON® ozone generator, as it demonstrates the ability to enhance the disinfection process of highly organic liquid effluents.

Bioaerosol disinfection using electro-ozonizers integrated into duct systems for hospital indoor air purification, using Klebsiella pneumoniae as an airborne bacterial model

In this work, an ozone gas stream is generated using PEM technology (MIKROZON® cell). Ozone is produced in an inert electrolyte through water oxidation, and then naturally transferred to a gaseous stream. The ozone quantity is regulated by adjusting the intensity to produce 0.02 mg min−1 at 0.05 A, 0.16 mg min−1 at 0.50 A, and 0.57 mg min−1 at 1.00 A. The effectiveness of the ozone gas stream is assessed in critical facilities such as hospitals for the inactivation of Klebsiella pneumoniae (K. pneumoniae) and the degradation of the blaKPC-11 gen in bioaerosols extracted from two scenarios: (1) bathrooms due to toilet flushing of urine or wastewater, and (2) other areas of hospitals, such as during emergencies when people’s saliva is atomized. An ozone mass flow of 0.57 mg min−1 was observed to alter the membrane permeability of K. pneumoniae cells, and as a result, blaKPC-11 removals of 1.27 and 0.93 logs are achieved for saliva and urine bioaerosols, respectively. Indeed, these treated air streams could be considered “acceptable” and “intermediate” for reintroduction into patient rooms to maintain thermal comfort, according to the standards set by the WHO expert group and the European Commission classification. The disinfection mechanisms of ozone are further studied, focusing on the competitive reactions that occur with the organic compounds present in the chemical composition of bioaerosols, with a significant impact on oligosaccharides.

Ozonation precipitation for iron removal in zinc hydrometallurgy

ABSTRACT Iron is an undesirable constituent and should be removed before zinc electrowinning. Oxidative precipitation using ozone for iron removal from ZnSO4 solution was investigated. Meanwhile, using air as an oxidant was compared at parallel tests. The results indicated that the per centage of iron removal is above two times higher using O3 than using air. With ozone, the effects of important process parameters, such as ZnO mass, temperature, O3 mass flow rate, time, and stirring speed, were systematically investigated. Under optimised conditions, i.e. MZnO/Fe of 1.45, temperature of 90°C, ozone mass flow rate of 3.12 g/h, 30 min, and stirring speed of 300 rev min−1, 99.98% of iron can be removed, causing 0.15% of Zn loss. The precipitate existed as good crystalline phases of FeOOH, MnO2 and ZnSO4·H2O, and composed of rough and dense particles with different size, which is beneficial for solid–liquid separation.

Treatment of Direct Red 23 in recirculating semi-pilot system by O3/UV process: Operational parameters effect and central composite design modeling

The treatment of C.I. Direct Red 23 (DR23) solution has been investigated by the ozonation under UV irradiation (O3/UV) in a recirculating semi-pilot mode. Decolorization efficiency (DE%) of DR23 was compared using the O3 and O3/UV processes, which was74.9% and 92.7% after 30-min treatment of the dye (100 mg/dm3), respectively. Then, the effect of experimental parameters on the O3/UV process including initial dye concentration, ozone mass flow rate and initial pH was studied. The obtained results revealed that the decolorization efficiency increased by enhancement of ozone amount and decreasing of the DR23 concentration; the decolorization process was performed efficiently at the basic condition (pH= 10) due to the production of extra hydroxyl radicals. The pseudo-first order kinetic was observed for the dye decolorization. Electrical energy per order decreases using the O3/UV process at the desired pH 10 indicating adequate synergistic effect of the photolysis and ozonation. Eventually, central composite design (CCD) approach was properly applied for prediction of the DE% with appropriate performance (R2 = 98.52%) and optimization of the process.

Real municipal wastewater treatment using simultaneous pre and post-ozonation combined biological attached growth reactor: Energy consumption assessment

In this study, simultaneous pre and post-ozonation processes combined biological attached growth reactor were used in order to investigate the removal of COD, ammonium and total coliforms from real municipal wastewater. The biological process was carried out in a fixed bed aerobic bioreactor with an aeration rate of 6 L/min and hydraulic retention time of 5 h. The ozonation process was performed simultaneously in pre-ozonation and post-ozonation reactors, with 1 g/h ozone mass flow within 30 min every 8 h. The results showed that complete ammonium removal and 94 % COD removal were obtained. Also, total coliforms in the final effluent were measured to be about 0.51 MPN/mL. The analysis of energy consumption showed that the ozonation process was the dominant energy consumption source. The combination of fixed bed bioreactor and ozonation process showed a promising technology for the treatment of real municipal wastewater.

Use of modified flotation cell as ozonation reactor to minimize mass transfer limitations

A novel approach based on high turbulence zones to minimize mass transfer limitation in ozonation and catalytic ozonation processes was investigated. A modified flotation cell (MFC), was used as a reactor because this device is widely used for application where three phases (solid-liquid-gas) must interact. Hydrodynamic parameters such as stirring rate, bubbles production and ozone dispersion were evaluated as well as the catalyst load, ozone mass flow, and catalyst reuse. The results show that by increasing the stirring rate in MCF, the ozone mass transfer coefficient enhanced. Under the best operating condition, complete caffeine degradation and mineralization of 57% is achieved in 20 min. It was demonstrated that the kinetic regime of ozonation for caffeine degradation in MFC was moderated, whereas in other reactors, this kinetic regimen is diffusional and even very slow. The ozone bubbles produced and dispersed have diameters between 1.32 and 1.98 mm. It was identified by using the scavenger that hydroxyl radical is generated in catalytic ozonation, and it is a key species for caffeine degradation and mineralization.

COD removal from disperse blue dye 79 in wastewater by using Ozone-Fenton process

Nowadays, one of the major problems that can face humankind is the water pollution. In this regard, making this natural resource a fresh and unpolluted is a major social and economic concern. However, a great attention has been given for the removal of organic pollutants discharged within wastewater by using advanced oxidation processes (AOPs) based on generation hydroxyl radicals. Among these, Ozone-Fenton (O3/H2O2/Fe2+) process used in this study as AOPs to remove chemical oxygen demand (COD) from Disperse Blue 79 (DB 79) dye in wastewater. Also, the effect of various experimental parameters such as ozone mass flow rate, mole ratio (mole H2O2/mole Fe2+), and reaction time on the COD removal efficiency of DB 79 were studied with constant initial concentration 60 mg/L of DB 79. Based on the results obtained in this study, the maximum COD removal efficiency was 85% achieved at optimum operating parameters are 288 mg/L. h ozone mass flow rate, 33.53 mole ratio (150 mg/L H2O2, 20 mg/L Fe2+), and 60 min reaction time. All Ozone-Fenton experiments were performed using Jar test apparatus at room temperature (23°C ∓ 2) and atmospheric pressure (1 atm). Finally, Ozone-Fenton offered an effective solution as AOPs for degrading pollutant especially DB 79 discharged within wastewater from various industrial processes.

Novel approaches based on hydrodynamic cavitation for treatment of wastewater containing potassium thiocyanate

Significant development in the industrial technologies and applications based on the use of cyanide derivatives has also led to significant environmental problems critically needing research in developing new technologies for effluent treatment. Present study investigates the use of novel treatment approach of hydrodynamic cavitation (HC) combined with chemical oxidation and catalyst for the degradation of Potassium Thiocyante (KSCN) for the first time. The effect of operating pressure (over the range of 2–5 bar) and initial pH (over the range of 2–7.1) on the degradation has been studied initially. Effect of combination of HC with H2O2 (varying KSCN:H2O2 ratios as 1:0.5–1:3), HC + O3 (varying ozone mass flow rate over the range of 200–400 mg/h), HC + O3 + catalyst (TiO2/ZnO/CuO at fixed loading of 0.1 g/L at optimized ozone flow rate) as process intensifying approaches on the KSCN degradation has also been studied. Combination of HC + O3 + CuO at different loadings of CuO has also been investigated. Use of combination of HC with H2O2 and HC with Ozone resulted in extent of KSCN degradation as 73% and 71.1% respectively. Among the different combinations of HC + O3 + Catalysts (TiO2/ZnO/CuO), HC + O3 + CuO (at loading of 0.15 g/l) resulted in highest KSCN degradation as 86.5%. Combination of HC + H2O2 + O3 + CuO was established to be the best approach yielding complete degradation with synergistic index of 2.98 and 92.9% as the COD removal. The study also focused on establishing kinetic rate constants which revealed that all the approaches followed first order mechanism with higher rate constants for the combination approaches as compared to individual approach. Overall, it has been conclusively established that hydrodynamic cavitation based combined treatment schemes are very effective for the treatment of biorefractory wastewaters containing cyanide derivatives.

Optimization of peroxone reaction rate using metaheuristic approach in the dearomatization and discoloration process

The main objective of this research focused on the optimization of apparent reaction rate constants (kapp) for degradation of a diazo compound, reactive yellow 42 (RY42) using peroxone reaction. Artificial Neural Network (ANN) was adopted to evaluate the effects of initial RY42 concentration, influent ozone mass flow rate, initial ozone (O3)/peroxide hydrogen ratio (H2O2), and pH on the discoloration rate constant. A proposed model by ANN was chosen after analysis of the topology based on R‐square (R2) and mean squared error (MSE) criteria followed by coupling the obtained best net with a novel evolutionary algorithm named Cuckoo Optimization Algorithm (COA). Although the relative importance of pH and O3/H2O2 on kapp was at the same level (about 18%), initial dye concentration (34%), and influent ozone mass flow rate (30%) were the most important factors. A systematic ANN‐COA approach indicated that the optimum values of pH and O3/H2O2 for 150 mg L−1 of RY42 were 7.5 and 1.44 L h−1, respectively, resulted in relatively different kapp for decolorization (0.18 min−1) and dearomatization (0.056 min−1). To confirm the validity of kinetic analysis, the predicted values were correlated with experimental values, which indicated the high degree of accuracy (R2= 0.98) for optimization of the peroxone process. This research with the experimental and modeling studies can be used as a guide for the design of full‐scale treatment processes for various types of industrial wastewater containing aromatic compounds with diazo groups. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 695–702, 2018

Modeling and kinetics study of acid anthraquinone oxidation using ozone: energy consumption analysis

An anthraquinone dye as a persistent organic material was eliminated by an environmentally safe method. In this work, decolorization of acid green 25 (AG25) was carried out using ozonation in a semibatch bubble column. Results showed that the process efficiency was affected by three operational parameters of influent ozone mass flow, initial AG25 concentration, and reaction time. Moreover, inhibitory effects of ethanol, 2-propanol, and carbonate as scavengers on the process efficiency were also evaluated. Kinetics study indicated that AG25 removal was a pseudo first-order reaction with respect to various concentrations of AG25, ozone, and radical scavenger. An artificial neural network (ANN) was developed to predict the process performance. The obtained weights from ANN were used for sensitivity analysis of the process. This analysis indicated that relative importance of influent ozone mass flow, initial AG25 concentration, and reaction time was 22, 14, and 64 %, respectively. Cost-effectiveness analysis of the process was implemented by calculating electrical energy consumption at various concentrations of AG25. Based on the results, the range of electrical energy consumption was found between 1.2 and 2.3 kWh/m3/order.

Post-Treatment of Composting Leachate by Ozonation

The post-treatment of composting leachate via an ozonation process in laboratory scale was studied in batch mode. According to the experiments, the COD removal was 47% after 30 min of ozonation via 0.4 g/h ozone (equivalent to 2.8 mg O3/mg COD removed) at pH 9. In this circumstance, the removal of color and turbidity was also 86% and 89%, respectively. Increasing the ozone mass flow rate higher than 0.4 g/h had no considerable effect on the process variables. However, increasing the reaction time had a significant effect on both the removal of color and on COD of the leachate. Experimental data indicated that complete removal of color and 51% removal of COD were achieved after about 40 min of ozonation via 0.4 g/h ozone (equivalent to 3.3 mg O3/mg COD removed). The ozone consumption rate increased as the reaction progressed and reached 4.1 mg O3/mg COD removed after 60 min.

Recovery of MnO2 from a spent alkaline battery leach solution via ozone treatment

This work investigates the reaction rate of Mn(II) to generate solid manganese dioxide (MnO2) as a function of the gaseous ozone mass flow rate (27.5–77 g h−1). The experimental studies were carried out in a semi-continuous reactor, using a synthetic solution (300 mL of 1 M H2SO4 with 6000 ppm of Mn(II) added as MnSO4) that simulated the composition of an acid leaching solution from spent alkaline battery material (SBM). It was observed that at 1.3–1.45 V/SHE and pH < 1.0 a selective formation of MnO2 powder was obtained; at values greater than 1.45 V/SHE, permanganate ion (MnO41−) was formed. On the other hand, a linear relation was perceived between the volumetric mass transfer coefficient (kLa) and the ozone mass flow rate (19.3–77 g h−1 in 600 mL of the 1 M H2SO4 solution). The rate constant (k) was determined in the presence and absence of nonporous plastic spheres (D = 3 mm). In both cases the rate of Mn(II) conversion increased proportionally with the ozone mass flow rate, although the conversions obtained with non-porous plastic spheres (x = 82%) were always higher than those without non-porous plastic spheres (x = 72%). A pseudo-homogenous mass transfer model adequately approximated the experimental data.

Color removal of distillery wastewater by ozonation in the absence and presence of immobilized iron oxide catalyst

Ozone is a strong oxidant, which can oxidize both biodegradable and non-biodegradable organics. The main objective of this study was to use iron oxide as a heterogeneous catalyst to enhance the ozone oxidation process. The wastewater used in this study was distillery wastewater, which was diluted 20 times before use. The diluted distillery wastewater was fed continuously in a downflow direction in an ozonation column. The iron oxide catalyst was coated on 10.3 mm diameter alumina balls (5.5 m 2/g specific surface area) by using Fe(NO 3) 3 as a precursor. The prepared catalyst was in the form of ferric oxide, and its loading was 0.07%. From the experimental results of both with and without the iron oxide catalyst, an increase in hydraulic retention time resulted in an increase in the treatment efficiencies of both chemical oxygen demand (COD) and color reduction, since the residence time of ozone increased. When the ozone mass flow rate increased, both COD and color reduction increased, resulting from an increase in the hydroxyl radical available in the system. The ozonation system with the iron oxide catalyst gave the highest efficiency in both COD and color removals because the hydroxyl free radical generated from the catalyst is more reactive than the ozone molecule itself.

Continuous ozonation of biologically pretreated molasses fermentation effluents

In this work, continuous chemical oxidation processes (single ozonation and ozone combined with hydrogen peroxide) of biologically pretreated wastewaters from a beet molasses fermentation factory have been studied. Oxidation processes were carried out in a stirred tank reactor at the natural pH of the wastewater and 25°C, analyzing the effect of the hydraulic residence time and applied ozone mass flow on color and organic matter removals. Ozone consumption was also measured in each experiment. The results show that continuous ozonation was effective for decolorization of molasses wastewater. Operating with a hydraulic residence time of 45 minutes and an applied ozone mass flow of 1.7 g/h, color and chemical oxygen demand (COD) reductions were about 80% and 14%, respectively. Increasing the hydraulic residence time or ozone mass flow led to a considerably increase in the ozone consumption, with similar color and organic matter reduction percentages. Slightly higher removal percentages were obtained combining ozone with hydrogen peroxide, attaining 83% color reduction and 20% COD removal. As consequence of the oxidation processes, biodegradability of the decolorized effluent increased about 40–50% and the ratio BOD5/COD was twofold higher.

SIMAZINE REMOVAL FROM WATER IN A CONTINUOUS BUBBLE COLUMN BY O3 AND O3/H2O2

Simazine, [2-chloro, 4,6-bis(ethylamino)-1,3,5-s-triazine], a common herbicide found in surface and ground water has been ozonized in continuous flow mode. Typical operating variables in ozonation processes have been investigated. Thus, the ozone dose fed to the system exerted a positive effect, while the gas flow rate did not influence the efficiency of the process provided ozone mass flow rate was kept constant. Increasing the pH led to a higher extension of the free radical degradation of simazine and, therefore, to a higher efficiency of the process. Also, addition of free radical promoters, i.e. hydrogen peroxide, did result in a significant improvement of the simazine removal rate. A first approach to process economy showed the system ozone/hydrogen peroxide as the most advantageous in terms of electrical energy requirements.

Atrazine removal by ozonation processes in surface waters

Atrazine (6‐chloro‐N‐ethyl‐N'‐isopropyl‐1,3,5‐triazinedyl‐2,4‐diamine) was treated with ozone alone and in combination with hydrogen peroxide or UV radiation in three surface waters. Experiments were carried out in two bubble reactors operated continously. Variables investigated were the ozone partial pressure, temperature, pH, mass flow ratio of oxidants fed: hydrogen peroxide and ozone and the type of oxidation including UV radiation alone. Residence time for the aqueous phase was kept at 10 min. Concentrations of some intermediates, including deethylatrazine, deisopropylatrazine and deethyldeisopropylatrazine, were also followed. The nature of water, specifically the alkalinity and pH were found to be important variables that affected atrazine (ATZ) removal. Surface waters with low alkalinity and high pH allowed the highest removal of ATZ to be reached. There was an optimum hydrogen peroxide to ozone mass flow ratio that resulted in the highest ATZ removal in each surface water treated. This optimum was above the theoretical stoichiometry of the process. Therefore, to reach the maximum removal of ATZ in a O3/H2O2 process, more hydrogen peroxide was needed in the surface waters treated than in ultrapure water under similar experimental conditions. In some cases, UV radiation alone resulted in the removal of ATZ higher than ozonation alone. This was likely due to the alkalinity of the surface water. Ozonation and UV radiation processes yield different amounts of hydrogen peroxide. Combined ozonations (O3/H2O2 and O3/UV) lead to ATZ removals higher than single ozonation or UV radiation but the formation of intermediates was higher.