Ozonation System Research Articles

Atmospheric isoprene ozonolysis: impacts of stabilised Criegee intermediate reactions with SO<sub>2</sub>, H<sub>2</sub>O and dimethyl sulfide

Abstract. Isoprene is the dominant global biogenic volatile organic compound (VOC) emission. Reactions of isoprene with ozone are known to form stabilised Criegee intermediates (SCIs), which have recently been shown to be potentially important oxidants for SO2 and NO2 in the atmosphere; however the significance of this chemistry for SO2 processing (affecting sulfate aerosol) and NO2 processing (affecting NOx levels) depends critically upon the fate of the SCIs with respect to reaction with water and decomposition. Here, we have investigated the removal of SO2 in the presence of isoprene and ozone, as a function of humidity, under atmospheric boundary layer conditions. The SO2 removal displays a clear dependence on relative humidity, confirming a significant reaction for isoprene-derived SCIs with H2O. Under excess SO2 conditions, the total isoprene ozonolysis SCI yield was calculated to be 0.56 (±0.03). The observed SO2 removal kinetics are consistent with a relative rate constant, k(SCI + H2O) / k(SCI + SO2), of 3.1 (±0.5) × 10−5 for isoprene-derived SCIs. The relative rate constant for k(SCI decomposition) / k(SCI+SO2) is 3.0 (±3.2) × 1011 cm−3. Uncertainties are ±2σ and represent combined systematic and precision components. These kinetic parameters are based on the simplification that a single SCI species is formed in isoprene ozonolysis, an approximation which describes the results well across the full range of experimental conditions. Our data indicate that isoprene-derived SCIs are unlikely to make a substantial contribution to gas-phase SO2 oxidation in the troposphere. We also present results from an analogous set of experiments, which show a clear dependence of SO2 removal in the isoprene–ozone system as a function of dimethyl sulfide concentration. We propose that this behaviour arises from a rapid reaction between isoprene-derived SCIs and dimethyl sulfide (DMS); the observed SO2 removal kinetics are consistent with a relative rate constant, k(SCI + DMS) / k(SCI + SO2), of 3.5 (±1.8). This result suggests that SCIs may contribute to the oxidation of DMS in the atmosphere and that this process could therefore influence new particle formation in regions impacted by emissions of unsaturated hydrocarbons and DMS.

Catalytic ozonation of simulated textile dyeing wastewater using mesoporous carbon aerogel supported copper oxide catalyst

Textile dyeing uses large amount of freshwater and synthetic dyes. Its effluents have to be subjected to certain treatments to remove the contaminants, especially for residue dyestuffs, before discharging to water bodies for elimination of adverse impacts to the environment. The objective of this research is to fabricate a novel catalyst, carbon aerogel supported copper oxide, and study its catalytic performance for the first time in ozonation of simulated dyeing wastewater for dye degradation. The catalyst was prepared using sol–gel and impregnation method, and characterized by Transmission Electron Microscope and X-Ray Diffraction techniques which suggesting that the nano-sized copper oxide particles successfully embedded and well-dispersed in the amorphous carbon aerogel. The catalytic performance of the catalyst was evaluated by degradation of C.I. Reactive Black 5 in a semi-continuous reactor. The results show that the catalyst has promising potential in ozonation towards dye elimination in dyeing wastewater, in which the dye removal efficiency can be effectively enhanced by the catalyst. In the specific conditions, COD removal could reach 46% in catalytic ozonation system after 60-min reaction, while it was only 29% in ozonation alone without catalyst. In addition, a systematic parameter study was performed to investigate the effect of the temperature, pH, ozone dosage, catalyst amount and dye concentration on dye degradation in terms of color and COD removal.

Quantum chemistry investigation on the reaction mechanism of the elemental mercury, chlorine, bromine and ozone system.

Ab initio calculations were performed to study the quantum chemistry reactions mechanisms among Hg(0), elemental halogen and O3. The geometry of reactions, transition states (TS), intermediates (M) and products were optimized using the MP2 method at the SDD basis function level for Hg, and using 6-311++G (3df, 3pd) for other species. Molecular energies were calculated at QCISD (T) level with zero point energy. Activation energies were calculated along with pre-exponential factors . The reaction rate constants within 298-1800K were calculated according to transition state theory (TST). The influences of O3 on the reaction of Hg(0) with halogen are discussed. Hg(0) can be oxidized to Hg(1+) by halogen and O3, and halogen and O3 can be arranged in decreasing order as: Br2 > BrO > O3 > Br > Cl, BrCl > HBr > HCl, Br2 > Cl2 according to reaction rate constants. When O3 is presented, Br2, HBr, BrCl, Cl2 and HCl react with O3 and are initially converted to BrO and ClO. O3 is unfavorable for oxidation of Hg(0) by Br2. The mixture of HBr and O3 has better oxidizing Hg(0) performance than HBr and O3. Cl is less effective than Br for oxidation of Hg(0).

Air-Fuel Ozonation System for a Combustion Engine Addressing an Environmental Target

The summary of results obtained in experimental studies to convert oxygen into ozone is discussed. The dependence of oxygen and ozone fuel burning is observed and optimized. The ozonation structure system for a combustion engine (CE) is developed. Adaptive automation system strategy is devised. The prototype model of ozone-ventilating device for a combustion engine fuel system is developed. The system is installed in the combustion engine. The analysis of exhaust gas concentration is performed applying an ozonizer and without it.

A review of indoor air treatment technologies

Indoor air pollution is a complex issue involving a wide diversity and variability of pollutants that threats human health. In this context, major efforts should be made to enhance indoor air quality. Thus, it is important to start by the control of indoor pollution sources. Nevertheless, when the suppression or minimization of emission sources is insufficient, technically unfeasible, or economically unviable, abatement technologies have to be used. This review presents a general overview of single treatment techniques such as mechanical and electrical filtration, adsorption, ozonation, photolysis, photocatalytic oxidation, biological processes, and membrane separation. Since there is currently no technology that can be considered fully satisfactory for achieving “cleaner” indoor air, special attention is paid to combined purification technologies or innovative alternatives that are currently under research and have not yet been commercialized (plasma-catalytic hybrid systems, hybrid ozonation systems, biofilter-adsorption systems, etc.). These systems seem to be a good opportunity as they integrate synergetic advantages to achieve good indoor air quality.

Catalytic ozonation of petroleum refinery wastewater utilizing Mn-Fe-Cu/Al2O 3 catalyst.

There is of great interest to develop an economic and high-efficient catalytic ozonation system (COS) for the treatment of biologically refractory wastewaters. Applications of COS require options of commercially feasible catalysts. Experiments in the present study were designed to prepare and investigate a novel manganese-iron-copper oxide-supported alumina-assisted COS (Mn-Fe-Cu/Al2O3-COS) for the pretreatment of petroleum refinery wastewater. The highly dispersed composite metal oxides on the catalyst surface greatly promoted the performance of catalytic ozonation. Hydroxyl radical mediated oxidation is a dominant reaction in Mn-Fe-Cu/Al2O3-COS. Mn-Fe-Cu/Al2O3-COS enhanced COD removal by 32.7% compared with a single ozonation system and by 8-16% compared with Mn-Fe/Al2O3-COS, Mn-Cu/Al2O3-COS, and Fe-Cu/Al2O3-COS. The O/C and H/C ratios of oxygen-containing polar compounds significantly increased after catalytic ozonation, and the biodegradability of petroleum refinery wastewater was significantly improved. This study illustrates potential applications of Mn-Fe-Cu/Al2O3-COS for pretreatment of biologically refractory wastewaters.

Rapid Removal of Nitrobenzene in a Three-Phase Ozone Loaded System with Gas–Liquid–Liquid

This study explores the removal rate of nitrobenzene (NB) using a new gas–liquid–liquid (G–L–L) three-phase ozone-loaded system consisting of a gaseous ozone, an aqueous solvent phase, and a fluorinated solvent phase (perfluorodecalin, or FDC). The removal rate of NB was quantified in relation to six factors including (1) initial pH, (2) initial NB dosage, (3) gaseous ozone dosage, (4) free radical scavenger, (5) FDC pre-aerated gaseous ozone, and (6) reuse of FDC. NB removal rate is positively affected by the first three of these factors. Compared with the conventional gas–liquid (water) (G–L) two-phase ozonation system, the free radical scavenger (tertiary butyl alcohol) has much less influence on the removal rate of NB in the G–L–L system. The FDC-loaded ozone acts as an ozone reservoir and serves as the main reactive phase in the G–L–L three-phase system. The reuse of FDC has little influence on the removal rate of NB. These experimental results suggest that the oxidation efficiency of ozonation in the G–L–L three-phase system is better than that in the conventional G–L two-phase system.

Effects of Semicontinuous and Batch System Ozonation on Wheat and Corn Starches

Wheat starch-water and corn starch-water suspensions (10%; w/w) were exposed to ozone gas by using two different contact systems; semicontinuous and batch systems. In semicontinuous contact mode, fresh ozone was applied to starch suspensions at a concentration of 4.2 mg dissolved ozone L−1 water for 30 min, while in closed batch contact mode, starch suspensions were stirred with ozone gas at a rate of 60 g/h for 30 min. Gelatinization temperatures and enthalpies of wheat and corn starch were increased in a semicontinuous system. However, no change was observed for the gelatinization characteristics of starch samples ozonated- in batch system. Structures and birefringences of wheat and corn starch ozonated in both semicontinuous and batch operations were not differentiated clearly. Higher lightness and whiteness values were observed for both wheat and corn starch ozonated in semicontinuous system than the controls and ozonated samples in batch system. Corn starch ozonated in semicontinuous system has lower chroma and yellowness values than the others. Total color difference for the samples ozonated in semicontinuous system is significantly different from the samples ozonated in batch system. Semicontinuous ozonation system is more effective on the thermal and color properties of wheat and corn starches than the batch ozonation system.

Can an ozone system generator reduce indoor triggers in asthmatic patient?

Can an ozone system generator reduce indoor triggers in asthmatic patient?

Water treatment efficacy of various metal oxide semiconductors for photocatalytic ozonation under UV and visible light irradiation

We have investigated a photocatalytic ozonation system of seven metal oxide semiconductors, TiO2 (P25), Nb2O5, SnO2, WO3, Fe2O3, In2O3, and BiVO4, under visible light both with and without UV irradiation for their efficacy in removing total organic carbon (TOC) from aqueous oxalic acid solution for water treatment. The investigation revealed that all the metal oxide samples functioned as photocatalysts for the photocatalytic ozonation system. TiO2 exhibited the highest activity under UV irradiation, and also exhibited a little activity under visible light irradiation. WO3, Fe2O3, In2O3, and BiVO4 functioned as visible-light-responsive photocatalysts and Fe2O3, In2O3, and BiVO4 were newly identified as active photocatalysts under visible light irradiation for the photocatalytic ozonation system. It is suggested that WO3 is a promising material for the photocatalytic ozonation system due to its activity in the wavelength range of solar energy.

Optimization and interpretation of O3 and O3/H2O2 oxidation processes to pretreat hydrocortisone pharmaceutical wastewater

Chemical synthetic pharmaceutical wastewater must be pretreated before traditional biological treatment to improve the biodegradability of pollutants due to their high concentration and complex composition. This study investigated O3 and O3/H2O2 systems to pretreat hydrocortisone wastewater. The optimum treatment efficiency of the O3 system was achieved under pH value of 5.76, dosage of O3 of 217.5 mg/L, and reaction time of 90 min. The removal efficiency of chemical oxygen demand (COD) and total organic carbon (TOC) was 94% and 92%, respectively. The ratio of biochemical oxygen demand (BOD) and COD (B/C) increased from 0.066 to 0.310. Moreover, the optimum H2O2/O3 molar ratio was 0.3 with the optimum pH of 3, and reaction time was reduced to 15 min to reach COD removal efficiency of 67.3% in the O3/H2O2 oxidation system. Interestingly, isobutanol was assumed to be a good hydroxyl radical trapping agent due to the great decrease of Fenton reagent reaction rate constant. By comparing two different kinetic models, oxidation mechanism could be interpreted by the pseudo first-order kinetic model with the high correlation coefficient R2 above 0.9787. It can be concluded that ozonation system was controlled by both direct oxidation and free radical oxidation, and particularly the later one played a dominant role.

Efficient degradation of nitrobenzene by an integrated heterogeneous catalytic ozonation and membrane separation system with active MgO(111) catalyst

An integrated heterogeneous catalytic ozonation and membrane separation system was studied for continuous degradation of refractory organic pollutants in water. MgO nanosheets with dominant (111) facets showed large amounts of medium and strong basic sites due to the particular structure of alternating monolayers of exclusively oxygen and exclusively magnesium atoms. MgO(111) acted as the ozonation catalyst for the first time, it was found that efficient degradation of nitrobenzene was achieved with 25.0 mmol/L of MgO(111) catalysts in a wide pH range of 4.0–12.0. In view of practical application, engineering problems to recover fine size catalysts from the treated water were resolved by applying membrane separation technology in the system. Experimental results showed that the membrane could successfully intercept MgO(111) particles in the reactor by the synergistic cooperative sieving of the bare and dynamic membranes. The long-term continuous experiments demonstrated that the removal rate of nitrobenzene could maintain over 90% with a constant flux of 3.92 L m−2 min−1 during the 24 h operation. The continuous system provides a new method for practical application of heterogeneous catalytic ozonation to remove refractory organic pollutants.

Photocatalytic Ozonation of Oxalic Acid Over Cu(II)-Grafted TiO2 Under Visible Light Irradiation

An efficient photocatalytic ozonation system that is sensitive to visible light was designed and fabricated over Cu(II)-grafted TiO2. The results show that oxalic acid was degraded efficiently in this system under visible light. This high efficiency was attributed to the synergetic effect of photocatalysis and ozonation, which facilitated the generation of holes on TiO2 and hydroxyl radicals. Moreover, Cu(II)-grafted TiO2 proved to be very stable in the reaction without any deactivation and the Cu ions would not leach from TiO2 to aqueous solution. Therefore, this photocatalytic ozonation system is promising to purify wastewater with refractory pollutants under visible light.

Regression Modeling of Ozonation Process in Wastewater Treatment Plants for Reduction of Waste Activated Sludge

This research was based on the hypothesis that waste activated sludge (WAS) from municipal wastewater treatment plants can be reduced by ozonation of excess biosolids to induce cell lysis and by promoting utilization of intracellular products released by ozonation of biosolids in the aeration basins. In this research, mathematical modeling studies were performed in order to define process design and major components of ozonation. The main purpose of the model simulations was to evaluate the effect of operational parameters of the ozonation system (such as dosage and duration of ozonation) and to determine the amount of solids to be ozonated in order to achieve desired mass reductions in WAS. This modeling study focused on identification of design parameters and their suggested range of operation. The model presented in this study does not intend to detail and analyze the impact of the scientific variables in the ozonation mechanism, nor does it try to model the biosolids destruction mechanisms when ozonation is applied. The computer model simulations indicated that zero biosolids yield conditions can be achieved if more biosolids than was grown on the influent wastewater was processed through the ozonation system. The simulations suggested that zero biosolids yield conditions can be observed if 2.4 times as much biosolids as was grown on the influent wastewater was processed through the ozonation column, with a daily R of about 0.08 mg O3/mg TSS-day. Furthermore, zero biosolids yield conditions can also be observed if only the amount of waste biosolids grown on the influent wastewater was processed through the ozonation column with a higher average daily R of 0.2 mg O3/mg TSS-day.

Disinfection methods and by-products formation

Water disinfection is a necessary process for the control of the pathogenic micro-organisms. However, the use of chemical disinfectants leads to the formation of disinfection by-products (DBPs). While the pathogenic micro-organisms are the primary cause of human health risk from water, DBPs also provide an unintended health hazard. Chlorination, chloramination, ozonation, and ultraviolet system are the most common methods used for drinking water and wastewater treatment. However, trihalomethanes (THMs), halogenic acetic acids, haloacetonitrils (HAN), halo-aldehydes and haloketons consist mainly of DBPs. Different types of DBPs are formed depending on a number of significant factors related to the selected method. The overall purpose of this paper was to analyze several disinfection method and compare the results of each one.

Inhibition of polymer formation in electrochemical degradation of p-nitrophenol by combining electrolysis with ozonation

Degradation of p-nitrophenol (PNP) by electrolysis, ozonation, and their combined processes (electrolysis-O3) was investigated. While electrolysis degraded PNP completely in 6 h, it produced considerable amounts of polymer by-products (∼20% of the total organic carbon (TOC) of the original solution). By comparison, ozonation and electrolysis-O3 degraded PNP much faster (in ∼30 min) and produced no detectable polymers. TOC analyses showed that the combined eletrolysis-O3 process mineralized PNP and its degradation intermediates much more effectively (98% TOC removal at 1.5 h) than the individual electrolysis and ozonation processes (58% and 75% at 6 h, respectively). Combining electrolysis with ozonation can thus not only inhibit polymer formation during electrochemical degradation of PNP, but also enhance pollutant mineralization significantly. The results indicate that the combination of electrolysis and ozonation can provide a simple and effective way to improve the performance and efficiency of existing electrolysis and ozonation systems for phenolic wastewater treatment.

Sequential ozone advanced oxidation and biological oxidation processes to remove selected pharmaceutical contaminants from an urban wastewater

Sequential treatments consisting in a chemical process followed by a conventional biological treatment, have been applied to remove mixtures of nine contaminants of pharmaceutical type spiked in a primary sedimentation effluent of a municipal wastewater. Combinations of ozone, UVA black light (BL) and Fe(III) or Fe3O4 catalysts constituted the chemical systems. Regardless of the Advanced Oxidation Process (AOP), the removal of pharmaceutical compounds was achieved in 1 h of reaction, while total organic carbon (TOC) only diminished between 3.4 and 6%. Among selected ozonation systems to be implemented before the biological treatment, the application of ozone alone in the pre-treatment stage is recommended due to the increase of the biodegradability observed. The application of ozone followed by the conventional biological treatment leads high TOC and COD removal rates, 60 and 61%, respectively, and allows the subsequent biological treatment works with shorter hydraulic residence time (HRT). Moreover, the influence of the application of AOPs before and after a conventional biological process was compared, concluding that the decision to take depends on the characterization of the initial wastewater with pharmaceutical compounds.

Catalytic and photocatalytic ozonation of tert-butyl alcohol in water by means of falling film reactor: Kinetic and cost–effectiveness study

Abstract This study investigates the oxidation conditions and kinetics of TBA as a pollutant in aqueous solutions using two different advanced oxidation processes; catalytic ozonation in the dark (TiO 2 /O 3 ) and in the presence of UVA illumination (TiO 2 /O 3 /UVA). The oxidation experiments were conducted in deionised water and in a real wastewater sample using a falling film reactor. The utilised electrical energy per order ( E EO ) under different oxidation conditions was calculated to investigate the cost effectiveness of the studied oxidation processes with regard to the electrical energy consumed by the treatments. It was observed that the oxidation of TBA by photocatalytic ozonation systems follows pseudo-first-order kinetic with respect to the concentration of TBA. The presence of metallic ions and increase of ozone and TBA concentration in the oxidation medium led to an increase of the oxidation rate of TBA in water. Catalytic ozonation in the dark showed the best cost effectiveness among the other oxidation conditions in the degradation of TBA in wastewater, with a consumed electrical energy of 12 kW/m 3 order.

Activated carbon-enhanced ozonation of oxalate attributed to HO oxidation in bulk solution and surface oxidation: Effects of the type and number of basic sites

The objective of this work is to study the influence of the type and number of basic sites of activated carbon (AC) on the AC-enhanced ozonation of oxalate. A commercial activated carbon (AC) was thermally treated with N-2, H-2, and NH3 at different temperatures. The results of chemical and textural characterization of the original and modified ACs show that the specific surface area and number of basic sites generally increased with increasing treatment temperature, whereas the acidic oxygen-containing groups decreased. Nitrogen-containing groups formed after NH3 treatment. The oxalate removal rate increased in ozonation systems with modified ACs compared with that of systems with the original AC. Oxalate degradation increased when ACs with higher numbers of basic sites and larger specific surface areas were used, except for the AC treated under NH3 at 900 degrees C. Oxalate removal was attributed to surface oxidation and HO. oxidation in bulk solution. The former process was dominant in the ozonation system with 0.2 g/L AC at pH 7. The experimental results indicate pyrrole groups may enhance ozone decomposition to generate HO. in bulk solution, while pyridine groups possibly decreased the surface oxidation of oxalate. Other basic sites, such as basal planes and basic oxygen-containing groups, enhanced oxalate removal through surface oxidation, and indirectly weakened HO. oxidation of oxalate in bulk solution. (C) 2014 Elsevier B.V. All rights reserved.

Sünger Filtre İle Çamur Yoğunlaştırmada Ozonun Etkisi ve Maliyet Analizi

The ultimate disposal of wastewater sludge (biosolids) continues to be one of the most difficult and expensive problems in the field of wastewater engineering. Wastewater treatment plants generate different sludges, like primary settled sludge, waste activated sludge, chemical sludge and anaerobic sludge, according to their operating systems. These excess sludges have to be managed by reducing their volume and stabilizing them before their ultimate disposal. Generally used volume reduction methods are thickening and dewatering that are usually coupled with conditioning. Sludge thickening and dewatering require either a big capital investment or a big surface area. Moreover, most of the mechanical dewatering technologies use polymers to condition the sludge before dewatering. These polymers have high cost rendering the mechanical dewatering uneconomical. It is possible to handle more thickened and dewatered sludge by adding polymer and initial cost of this system is lower than ozonation system. Howewer it was found that ozonation had same effect and it would be more economical than polymer system after 11 years.