Ozone Addition Research Articles

Effect of different sludge reduction methods on sludge reduction rates, performance of activated sludge process and urban planning

Effect of biological methods (aerobic digestion, anaerobic digestion, and predation by Tubifex tubifex), physical methods (addition of uncoupling agent), and chemical methods (addition of ozone, chlorine) on the efficiency of sludge reduction was compared, so was the effect of different sludge reduction methods on the performance of activated sludge process with respect to the content and nature of organic matters. It was concluded that the best sludge reduction technology was using uncoupling agent with sludge reduction efficiency at 60%, followed by ozone, chlorine, micro-biological, aerobic biological, and anaerobic biological, which was the worst with efficiency at 36%. All of the molecular weight (MW) distribution of supernatant in activated sludge processes was changed to some extent under different sludge reduction methods. The change of the MW distribution would play a certain impact on the biodegradable ability of the organics, thus affecting the efficiency of sludge reduction rate. Finally, the impacts of final disposal method on urban environment were analyzed, and some recommendations related to urban planning were made.

Removal of dimethyl sulfide by the combination of non-thermal plasma and biological process

A bench scale system integrated with a non-thermal plasma (NTP) and a biotricking filtration (BTF) unit for the treatment of gases containing dimethyl sulfide (DMS) was investigated. DMS removal efficiency in the integrated system was up to 96%. Bacterial communities in the BTF were assessed by PCR-DGGE, which play the dominant role in the biological processes of metabolism, sulfur oxidation, sulfate-reducing and carbon oxidation. The addition of ozone from NTP made microbial community in BTF more complicated and active for DMS removal. The NTP oxidize DMS to simple compounds such as methanol and carbonyl sulfide; the intermediate organic products and DMS are further oxidized to sulfate, carbon dioxide, water vapors by biological degradation. These results show that NTP-BTF is achievable and open new possibilities for applying the integrated with NTP and BTF to odour gas treatment.

Simultaneous humic acid removal and bromate control by O3 and UV/O3 processes

Bromate is a potential carcinogen that forms during the treatment of bromide-containing water using ozone-based technologies. A study of humic acid (HA) removal and bromate formation in UV/O3 and ozone processes was conducted relative to a variety of operational conditions, such as ozone dosage, pH and initial concentrations of HA and Br−. Additionally, UV irradiation with the addition of ozone, which was generated by the same low-pressure mercury lamp (emitting 254nm and 185nm), was studied. Bromate concentrations during the UV/O3 process were 17.1–77.6μg/L, which was 2.1–2.9 times the concentration for the O3 process, when ozone at concentrations ranging from 1.5 to 6.3mg/L was continuously applied to water to which no HA was added. UV radiation reduced the concentration of the residual ozone, which was important for the formation of bromate. HA inhibited bromate formation, which was especially dramatic in UV/O3 process, and increasing the initial concentration of Br− accelerated the bromate formation in both processes; however, enhancement of bromate formation after increasing the pH was only observed for O3 process. Reducing the ozone dosage in UV/O3 process lessened both residual ozone concentration and hydroxyl radical (OH) exposure; changing this parameter led to a slight drop in the rate of HA removal but also caused a significant decrease in the bromate formation. Therefore, the combination of UV irradiation and low doses of ozone represented a promising method for the simultaneous control of bromate formation and HA removal. Because the UV lamp can also generate a low concentration of ozone, combining UV irradiation with the internally generated ozone is recommended.

Nano Membrane Water: development of innovative hybrid processes for contaminated water treatment using nanoporous membranes

This study aims at the development of a hybrid process for the efficient treatment of water and potentially of wastewater, by the combination of ozonation and membrane filtration and the investigation of the complete ozone utilization by the employment of a novel ceramic membrane reactor concept. The advantages of the process are mainly referred to the achievement of a homogeneous (down to microscale) transfer and distribution of ozone (“bubbles aeration”) within the main body of bulk water stream, which results in very efficient oxidation. Ceramic membranes were prepared initially, in order to investigate the single filtration of groundwater; tubular shaped nonsymmetric ceramic membranes were developed and their efficiency was examined for the removal of As-loaded water. Microporous γ-Al2O3–17Fe (molar ratio Al and Fe: 1:1) membrane was found to adsorb the pollutant As(V) ions up to 95%. The combined process of ozonation and membrane filtration was examined in a bench scale unit, where ozone was added through a ceramic diffuser at low flow rates, under continuous and intermittent modes. Simulated ground and surface water containing 25 mg L-1 of kaolin and humic acid was fed to the reactor; it was found that the intermittent mode of ozone addition was beneficial over the continuous mode of operation, resulting in lower trans-membrane pressure values. However, the hybrid process of ozonation-membrane filtration resulted in a lower quality effluent with a higher Total Organic Carbon content, possibly due to the effect of ozone on organic substances: ozone resulted to the dissociation of large molecular weight compounds and the formation of smaller molecules that could easily pass through the membranes in the effluent. In addition, a new hybrid ozone-filtration unit has been constructed. In this unit, the water to be treated flows through the inner side of a tubular membrane while gaseous ozone stream flows along the outer. An appropriate pressure drop gradient causes ozone to flow towards the inner water stream through the nanopores of the ceramic membrane, causing oxidation (and decomposition) of the organic substances or complexes, which are present in the water stream. The retentate stream of the first step represents the influent to the second step where the removal of ions is achieved by ceramic membranes (ultrafiltration).

Ozone-assisted UV254 nm photodegradation of gaseous ethylbenzene and chlorobenzene: Effects of process parameters, degradation pathways, and kinetic analysis

Ultraviolet photodegradation can destroy a wide range of organic compounds and has gained considerable interest for use in reducing environmental pollution. In the present study, ozone-assisted UV photodegradation was developed for the decomposition of gaseous ethylbenzene (EB) and chlorobenzene (CB). The effects of various experimental parameters were investigated, namely initial concentration, initial ozone addition, relative humidity, and reaction time. The results showed that an ozone/EB ratio of 2.5 and an ozone/CB ratio of 1.5 increased the conversion efficiencies 13.0 and 6.3 times, respectively, compared with photolysis alone. The relative humidities of the reaction media affected the target conversions, and also the dominant oxidizer in the conversion process (O3 for EB and hydroxyl radicals for CB). Possible pathways and mechanisms were suggested on the basis of the intermediates identified, some of which were more soluble and biodegradable than the target compounds. Two kinetic models, based on initial concentration and ozone addition, were developed to describe the EB and CB conversion behaviors. The preliminary results indicated that ozone-assisted photodegradation enhanced gaseous EB and CB decomposition, and that this could be a promising technology for the conversion of recalcitrant and insoluble volatile organic compounds.

Quantum chemical study of the addition of ozone to acetylene

The primary step of acetylene ozonation was studied by the B1LYP, PBE0, CASSCF, MRMP2, and CCSD methods using the 6-31+G**, aug-cc-pVDZ, cc-pVTZ, and aug-cc-pVTZ basis sets. The study confirmed the earlier B3LYP-based conclusions that the intermediate complex, as well as the transition states of the concerted addition (Criegee’s mechanism) and unconcerted addition (DeMore’s mechanism), are involved in this reaction event. The activation enthalpy and entropy and rate constants of the reaction were calculated. Criegee’s mechanism was shown to dominate in the reaction with acetylene, but the contribution from DeMore’s mechanism is also noticeable, being 1–8%.

Cycloaddition of ozone to allyl alcohol, acrylic acid and allyl aldehyde: A comparative DFT study

Density functional theory and ab initio methods have been used to calculate the structures and energies of minima and transition sates for the cycloadditions of ozone to allyl alcohol, acrylic acid and allyl aldehyde. The results show that the reactivity of the compounds with respect to addition of ozone to the double bond is a function of the nature of the oxygenated substituents. The acrylic acid is more reactive toward ozone than the corresponding allyl aldehyde, consistent with the relative magnitude of the electron-withdrawing influence of the substituent oxygenated groups. In comparison with acrylic acid and allyl aldehyde, the cycloaddition of ozone to allyl alcohol should be the most favored thermodynamically. Moreover, the calculated rate constants of the three cycloaddition reactions at the BH&HLYP/6-31+G(d,p) level of theory are in good agreement with experimental data.

Effects of acute single intranasal instillation of secondary organic aerosol on neurological and immunological biomarkers in the brain and lung of BALB/c mice

Recently, we have reported that primary particles from diesel exhaust affect nervous system, immune system, and learning ability in mice. Currently, in vivo and in vitro studies have shown that secondary organic aerosol (SOA) generated from the coal-fired power plant induced adverse effects in lung and heart. However, the effect of SOA on central nervous system is still unknown. In the present study, using potential biomarkers recognized in previous studies of primary particles, we investigated the effect of acute single administration of SOA on the expression levels of various biomarkers in the brain and lung of mice. We generated the SOA by addition of ozone (O(3)) to the diesel exhaust particle (DEP). Eight-week-old male BALB/c mice were administered DEP or DEP+O(3) (SOA) (50 µg/50 µl/mouse) intranasally. Twenty-four hour after acute single exposure to SOA, olfactory bulb, hippocampus and lung from all mice were collected and mRNA expressions of neurological and immunological biomarkers were examined using real-time RT-PCR analysis and histological examination. Proinflammatory cytokines, their transcription factor and neurotrophin mRNA were remarkably increased in lung of mice exposed to SOA but not in the brain. Microarray data showed that changes of the inflammatory reaction and metabolizing enzyme gene cluster were observed in the brain and lung. Our findings suggested that an acute single exposure of SOA does not affect biomarkers in the brain of normal healthy individuals. Our present results also clearly indicate that SOA induces inflammatory responses in the lung by modulating proinflammatory cytokines, transcription factor and inflammatory responsive neurotrophins.

Study of ozone-enhanced combustion in H2/CO/N2/air premixed flames by laminar burning velocity measurements and kinetic modeling

The enhancement effect of ozone addition for H2/CO/N2/Air premixed flames at ambient condition is investigated both experimentally and computationally. Adiabatic laminar velocities under different amount of O3 addition were directly measured using the Heat Flux Method. The ozone concentration in the oxidizer is monitored online to ensure the precise control and stability of ozone injection. Experimental data shows significant enhancement of the burning velocities due to O3 addition. With 8500 ppm ozone seeded, maximum 18.74% of burning velocity enhancement is observed at equivalence ratio Φ = 0.7. Kinetic modeling works were conducted by integrating ozone sub-mechanism with three kinetic mechanisms: GRI-Mech 3.0, Davis mechanism and USC Mech II. The modeling results were compared with experimental data. GRI-Mech 3.0 + Ozone mechanism demonstrated the ability to reproduce the experimental data. Extra OH radicals promoted by ozone was found in the pre-heat regime which initiates the chain-branching reaction and results in the combustion enhancement.

Ultrasonic-assisted ozone oxidation process of triphenylmethane dye degradation: Evidence for the promotion effects of ultrasonic on malachite green decolorization and degradation mechanism

This study aimed to prove the promotion effects of ultrasonic on malachite green (MG) decolorization in the ultrasonic-assisted ozone oxidation process (UAOOP), and propose the possible pathway of MG degradation. The decolorization of MG followed an apparent pseudo first-order kinetic law (initial MG concentration 100–1000mg/L). When ultrasonic (US) was applied with ozone simultaneously, the apparent pseudo-first-order rate constant (Kapp) increased, and the time MG decolorized to the half of initial concentration (T1/2) shortened 185s (1000mg/L). Moreover, the stoichiometric ratio (Zapp) between O3 and MG was enhanced by US to 2.0mol, saving 11% oxidant addition, comparing to individual ozone process. These results indicated that the application of US can reduce reaction time and dose of ozone addition. The possible pathway of MG degradation included three major approaches. And the result suggested that the reaction between MG and hydroxyl radical was substitution reaction rather than adduct reaction.

Reaction Probability and Infrared Detection of the Primary Ozonide in Collisions of O3 with Surface-Bound C60.

The kinetics and mechanism of reactions between gas-phase ozone and surface-bound C60 have been investigated by monitoring changes to reflection-absorption infrared spectra within a well-characterized film of C60 during exposure to a controlled flux of pure ozone. These ultrahigh vacuum studies provide direct infrared spectroscopic evidence for the formation and decomposition of a primary ozonide of C60. The spectral assignments of this highly unstable intermediate have been verified using electronic structure calculations. Theory and experiment revealed that C60 oxidized nearly exclusively via addition of ozone across the double bond that links two six-carbon-containing rings of the molecule. Following spectral characterization, the initial probability for ozone to react with the surface was found to be 5.8 ± 0.2 × 10(-4). Once formed, the ozonide quickly thermally decomposed to a variety of carbonyl-containing products.

Quantum Chemical Study of the Initial Step of Ozone Addition to the Double Bond of Ethylene

The mechanisms of the initial step in chemical reaction between ozone and ethylene were studied by multireference perturbation theory methods (MRMP2, CASPT2, NEVPT2, and CIPT2) and density functional theory (OPW91, OPBE, and OTPSS functionals). Two possible reaction channels were considered: concerted addition through the symmetric transition state (Criegee mechanism) and stepwise addition by the biradical mechanism (DeMore mechanism). Predicted structures of intermediates and transition states, the energies of elementary steps, and activation barriers were reported. For the rate-determining steps of both mechanisms, the full geometry optimization of stationary points was performed at the CASPT2/cc-pVDZ theory level, and the potential energy surface profiles were constructed at the MRMP2/cc-pVTZ, NEVPT2/cc-pVDZ, and CIPT2/cc-pVDZ theory levels. The rate constants and their ratio for reaction channels calculated for both mechanisms demonstrate that the Criegee mechanism is predominant for this reaction. These results are also in agreement with the experimental data and previous computational results. The structure of DeMore prereactive complex is reported here for the first time at the CCSD(T)/cc-pVTZ and CASPT2/cc-pVDZ levels. Relative stability of the complexes and activation energies were refined by single-point energy calculations at the CCSD(T)-F12/VTZ-F12 level. The IR shifts of ozone bands due to formation of complexes are presented and discussed.

Thermochemical analysis and kinetics aspects for a chemical model for camphene ozonolysis

In this work, a chemical model for the camphene ozonolysis, leading to carbonyl final products, is proposed and discussed on the basis of the thermochemical properties and kinetic data obtained at density functional theory levels of calculation. The mechanism is initiated by the electrophilic attack of ozone to the double bond in camphene leading to a 1,2,3-trioxolane intermediate, which decomposes to peroxy radicals and carbonyl compounds in a total of 10 elementary reactions. The thermodynamic properties (enthalpy and entropies differences) are calculated at 298 K. For the thermochemical evaluation, theoretical calculations are performed with the B3LYP, MPW1PW91, and mPW1K density functionals and the basis sets 6-31G(d), 6-31G(2d,2p), 6-31+G(d,p), and 6-31+G(2d,2p). Eventually, single point calculations adopting the 6-311++G(2d,2p) basis set are performed in order to improve the electronic energies. The enthalpy profiles suggest highly exothermic reactions for the individual steps, with a global enthalpy difference of -179.18 kcal mol(-1), determined at the B3LYP∕6-31+G(2d,2p) level. The Gibbs free energy differences for each step, at 298 K, calculated at the B3LYP∕6-311++G(2d,2p)∕∕B3LYP∕6-31+G(2d,2p) level, are used to estimate the composition of a final product mixture under equilibrium conditions as 58% of camphenilone and 42% of 6,6-dimethyl-ɛ-caprolactone-2,5-methylene. For the reaction kinetics, the bimolecular O(3) + camphene step is assumed to be rate determining in the global mechanism. A saddle point for the ozone addition to the double bond is located and rate constants are determined on the basis of the transition state theory. This saddle point is well represented by a loosely bound structure and corrections for the basis set superposition error (BSSE) are calculated, either by considering the effect over the geometry optimization procedure (here referred as CP1 procedure), or the effect of the BSSE over the electronic energy of a previously optimized geometry, included a posteriori (here referred as CP2). The rate constants, calculated at 298 K from the data obtained at the mPW1K∕6-31+G(d,p), CP1∕B3LYP∕∕6-31+G(2d,2p), and CP2∕B3LYP∕∕6-31+G(2d,2p) levels (3.62 × 10(-18), 1.12 × 10(-18), and 1.39 × 10(-18) cm(3) molecule(-1) s(-1)), are found in good agreement with the available experimental data at the same temperature, 0.9 × 10(-18) cm(3) molecule(-1) s(-1) [R. Atkinson, S. M. Aschmann, and J. Arey, Atmos. Environ. 24, 2647 (1990)]. The importance of the BSSE corrections for the final rate constants must be pointed out. Furthermore, this work will contribute to a better understanding of the chemistry of monoterpenes in the atmosphere, as well as the implications for the phenomena of pollution.

THE ONSET OF GOITER IN SEVERAL SPECIES OF SHARKS FOLLOWING THE ADDITION OF OZONE TO A TOUCH POOL

This report describes the onset of goiter in several species of shark following the addition of ozone to a touch pool. A detailed description of a female brown-banded bamboo shark (Chiloscyllium punctatum) that was presented with multinodular goiter is provided. Four other brown-banded bamboo sharks and 11 white-spotted bamboo sharks (Chiloscyllium plagiosum) housed in the same system developed clinical disease consistent with goiter, but two zebra bullhead sharks (Heterodontus zebra) did not. Plasma thyroxine (T4) concentration was 4.64 ng/ml before euthanasia, consistent with a diagnosis of hypothyroidism. The sharks had been chronically exposed to mean (+/- standard error) NO3-N concentrations of 35 +/- 5.12 mg/L before ozonation of the system. Ozonation of aquarium water causes a reduction in environmental iodide, which is required for thyroid hormone synthesis. Nitrate is goitrogenic and would further decrease I- absorption by competitive inhibition. Multinodular goiter is consistent with goiter caused by chronic iodide deficiency. Understanding the interaction between water chemistry and goiter development is critical to development of elasmobranch health management systems.

UV-based advanced oxidation processes for the treatment of odour compounds: Efficiency and by-product formation

The occurrence of the taste and odour compounds geosmin and 2-methyl isoborneol (2-MIB) affects the organoleptic quality of raw waters from drinking water reservoirs worldwide. UV-based oxidation processes for the removal of these substances are an alternative to adsorption and biological processes, since they additionally provide disinfection of the raw water. We could show that the concentration of geosmin and 2-MIB could be reduced by VUV irradiation and the combination of UV irradiation with ozone and hydrogen peroxide in pure water and water from a drinking water reservoir. The figure of merit EE/O is an appropriate tool to compare the AOPs and showed that VUV and UV/O3 yielded the lowest treatment costs for the odour compounds in pure and raw water, respectively. Additionally, VUV irradiation with addition of ozone, generated by the VUV lamp, was evaluated. The generation of ozone and the irradiation were performed in a single reactor system using the same low-pressure mercury lamp, thereby reducing the energy consumption of the treatment process. The formation of the undesired by-products nitrite and bromate was investigated. The combination of VUV irradiation with ozone produced by a VUV lamp avoided the formation of relevant concentrations of the by-products. The internal generation of ozone is capable to produce ozone concentrations sufficient to reduce EE/O below 1 kWh m−3 and without the risk of the formation of nitrite or bromate above the maximum contaminant level.

Photocatalytic decomposition of gaseous 1,2-dichlorobenzene on TiO2 films: Effect of ozone addition

Gaseous 1,2-dichlorobenzene (1,2-DCBz) was photocatalytically decomposed on a powdered TiO2 layer using UV-light, or the latter combined with ozone addition. The effect of various experimental parameters was studied, including inlet concentrations of ozone, UV irradiation or not, carrier gas (dry air or nitrogen) and treatment time period. A temperature of 150°C is selected, to replicate flue gas conditions after bag house filter. An optimum ozone addition of ca. 165ppm was established, higher concentrations barely improving photocatalytic removal. Possible pathways and mechanisms are discussed on the basis of the intermediate products identified, the chloride ions distribution in the effluent and catalyst surface, and a carbon conversion balance.

Efficient Photocatalytic Decomposition of Perfluorooctanoic Acid by Indium Oxide and Its Mechanism

Perfluorooctanoic acid (C(7)F(15)COOH, PFOA) has increasingly attracted worldwide concerns due to its global occurrence and resistance to most conventional treatment processes. Though TiO(2)-based photocatalysis is strong enough to decompose most organics, it is not effective for PFOA decomposition. We first find that indium oxide (In(2)O(3)) possesses significant activity for PFOA decomposition under UV irradiation, with the rate constant about 8.4 times higher than that by TiO(2). The major intermediates of PFOA were C(2)-C(7) shorter-chain perfluorocarboxylic acids, implying that the reaction proceeded in a stepwise manner. By using diffuse reflectance infrared Fourier transform spectroscopy, (19)F magic angle spinning nuclear magnetic resonance, and electron spin resonance, we demonstrate that the terminal carboxylate group of PFOA molecule tightly coordinates to the In(2)O(3) surface in a bidentate or bridging configuration, which is beneficial for PFOA to be directly decomposed by photogenerated holes of In(2)O(3) under UV irradiation, while PFOA coordinates to TiO(2) in a monodentate mode, and photogenerated holes of TiO(2) preferentially transform to hydroxyl radicals, which are inert to react with PFOA. PFOA decomposition in wastewater was inhibited by bicarbonate and other organic matters; however, their adverse impacts can be mostly avoided via pH adjustment and ozone addition.

Kinetic study on the linalool ozonolysis reaction in the atmosphere

In the atmosphere, linalool ozonolysis will generate a series of oxidation products and then form particles through nucleation. In this study, the linalool ozonolysis mechanisms were studied and some of the main products detected from experiment are verified. The Rice–Ramsperger–Kassel–Marcus (RRKM) theory and the canonical variational transition state theory (CVT) with small curvature tunneling effect (SCT) are used to calculate rate constants over the temperature range of 200∼800 K. The total rate constant for the reaction of ozone with linalool is 4.50 × 10−16 cm3 molecule–l s–l, and the addition of ozone to (CH3)2C=CH– is the main ozone addition position. Furthermore, the Arrhenius formulas are fitted and the lifetimes of reaction species in the troposphere are discussed for the first time. The total atmospheric lifetime of linalool relative to O3 is 2.30 h. The O3-initiated atmospheric lifetimes of P1, P3, and P6 are 2.64 months, 16.67 days, and 15.5 h, respectively.

Molecular dynamics simulation of adsorption of ozone and nitrate ions by water clusters

Coadsorption of ozone molecules and nitrate ions by water clusters was studied by the molecular dynamics technique. The maximum value of an average O-H…O bond length in a water carcass is realized at the minimum specific number of such bonds when the ratio of adsorbed ozone molecules to nitrate ions captured by a cluster is two. IR absorption and reflection spectra were reshaped significantly, and new peaks appeared at Raman spectra due to the addition of ozone and nitrate ions to the disperse water system. After ozone and nitrate ions were captured, the average (in frequency) IR reflection coefficient of the water disperse system increased drastically and the absorption coefficient fell.

Ultrasonic Degradation of p-Nitrophenol in the Presence of Additives at Pilot Scale Capacity

In the present work, the efficacy of the ultrasonic reactors for the degradation of p-nitrophenol, one of the most refractory compounds, has been investigated at pilot scale operation. An attempt has also been made to intensify the degradation process using different additives. The effect of air sparging, CCl4 addition, addition of solid particles such as TiO2 and CuO, and addition of ozone on the extent of degradation of p-nitrophenol has been studied. The sonochemical reactor used in the work is an ultrasonic longitudinal horn type reactor operating at 25 kHz frequency, power output of 1 kW, and capacity of 7 L. It has been observed that the extent of degradation increased for all the additives used in the present study possibly attributed to enhanced cavitational activity and generation of additional free radicals or oxidizing species. Maximum degradation of 93.5% was obtained using CCl4 as an additive at an optimum loading of 1 g/L. It appears that among different additives, additives giving additional free radicals and parallel oxidation mechanisms give more intensification as compared to additives which only enhance the cavitational activity in the system. It has been established that the use of additives at optimum concentration, which is dependent on the inherent cavitational activity in the reactor, results in significant intensification of the degradation process.