Ozone-Based Advanced Oxidation Processes for the Decomposition of N-Methyl-2-Pyrolidone in Aqueous Medium

The present study investigates the decomposition of N-Methyl-2-Pyrolidone (NMP) using conventional ozonation (O₃), ozonation in the presence of UV light (UV/O₃), hydrogen peroxide (O₃/H₂O₂), and UV/H₂O₂ processes under various experimental conditions. The influence of solution pH, ozone gas flow dosage, and H₂O₂ dosage on the degradation of NMP was studied. All ozone-based advanced oxidation processes (AOPs) were efficient in alkaline medium, whereas the UV/H₂O₂ process was efficient in acidic medium. Increasing ozone gas flow dosage would accelerate the degradation of NMP up to certain level beyond which no positive effect was observed in ozonation as well as UV light enhanced ozonation processes. Hydrogen peroxide dosage strongly influenced the degradation of NMP and a hydrogen peroxide dosage of 0.75 g/L and 0.5 g/L was found to be the optimum dosage in UV/H₂O₂ and O₃/H₂O₂ processes, respectively. The UV/O₃ process was most efficient in TOC removal. Overall it can be concluded that ozonation and ozone-based AOPs are promising processes for an efficient removal of NMP in wastewater.     

Treatment of Jewelry Manufacturing Effluent Containing Cyanide Using Ozone-Based Photochemical Advanced Oxidation Processes

This article considers Advanced Oxidation Processes involving O₃, O₃/UV, O₃/H₂O₂/UV, and H₂O₂/UV to destroy cyanide in jewelry manufacturing wastewaters. All experiments were performed in a semibatch reactor. The results showed that total cyanide can be reduced with different reaction rates, and the decrease of total cyanide can be described by pseudo–first-order kinetics. The reaction was performed under different pH values and H₂O₂ dosages to find the optimal conditions for the oxidation processes. The ozonation process destroyed total cyanide faster at a pH = 12, whereas ozonation combined with H₂O₂ and/or UV destroyed cyanide faster at a pH =10. The total cyanide destruction rate in the UV/H₂O₂ (700 mg/L) treatment was the highest among all studied processes, with removal efficiencies of 99% for CN^?, 99% for COD and 99% for TOC.     

Post-Treatment of Pulp and Paper Industry Wastewater by Advanced Oxidation Processes

The aim of this study was to investigate the effectiveness of chemical oxidation by applying ozonation, combination of ozone and hydrogen peroxide and Fenton's processes for decolorization and residual chemical oxygen demand (COD) removal of biologically pretreated pulp and paper industry effluents. The batch tests were performed to determine the optimum operating conditions including pH, O₃, H₂O_2, and Fe²⁺ dosages. H₂O₂ addition reduced the reaction times for the same ozone dosages; however combinations of ozone/hydrogen peroxide were only faintly more effective than ozone alone for COD and color removals. In the Fenton‘s oxidation studies, the removal efficiencies of COD, color and ultraviolet absorbance at 254 nm (UV₂₅₄) for biologically treated pulp and paper industry effluents were found to be about 83, 95, and 89%, respectively. Experimental studies indicated that Fenton oxidation was a more effective process for the reduction of COD, color, and UV₂₅₄when compared to ozonation and ozone/hydrogen peroxide combination. Fenton oxidation was found to have less operating cost for color removal from wastewater per cubic meter than the cost for ozone and ozone/hydrogen peroxide applications.     

Removal of diazinon by various advanced oxidation processes

Diazinon is a widely used organophosphorus insecticide that is an important pollutant in aquatic environments. The chemical removal of diazinon has been studied using UV radiation, ozone, Fenton's reagent, UV radiation plus hydrogen peroxide, ozone plus hydrogen peroxide and photo‐Fenton as oxidation processes. In the photodegradation process the observed quantum yields had values ranging between 2.42 × 10^?2 and 6.36 × 10^?2 mol E^?1. Similarly, the ozonation reaction gave values for the rate constant ranging between 0.100 and 0.193 min^?1. In the combined systems UV/H₂O₂ and O₃/H₂O₂ the partial contributions to the global oxidation reaction of the direct and radical pathways were deduced. In the Fenton's reagent and photo‐Fenton systems, the mechanism of reaction has been partially discussed, and the predominant role of the radical pathway pointed out. Additionally, the rate constant for the reaction between diazinon and the hydroxyl radicals was determined, with the value 8.4 × 10⁹ L mol^?1 s^?1 obtained. A comparison of the different oxidation systems tested under the same operating conditions revealed that UV radiation alone had a moderate oxidation efficiency, which is enhanced in the case of ozone, while the most efficient oxidant is the photo‐Fenton system. Copyright © 2007 Society of Chemical Industry     

Chemical treatment of cork‐processing wastewaters for potential reuse

The chemical treatment of cork‐processing wastewater by ozonation, alone and in combination with hydrogen peroxide and UV radiation was investigated. A reduction of the chemical oxygen demand (COD) ranging from 42% to 76% was obtained during ozonation after 3 h of reaction, depending on the experimental conditions. The additional presence of hydrogen peroxide and UV radiation enhanced the efficiency of the ozonation treatment due to the contribution of the OH radicals formed in the decomposition of ozone. Thus, final reductions of the COD higher than 90% and a complete elimination of phenolic compounds and absorbance at 254 nm were achieved in both Advanced Oxidation Processes (AOPs), O₃/H₂O₂ and O₃/UV. Therefore the effluent resulting from the ozonation treatments can be reused in the cork‐processing industry. In a second step, the chemical treatment was conducted by means of UV radiation alone and by the action of hydroxyl radicals, which were generated by the following AOPs: UV/H₂O₂, Fenton's reagent, and photo‐Fenton system. The single photochemical process resulted in 9% of the organic matter present being removed, while the AOPs significantly enhanced this reduction with values in the range 20–75%. Kinetic studies for both groups of treatments were performed, and apparent kinetic rate constants were evaluated. In the ozone‐based experiments, the rate constants ranged from 1846 to 10922 dm³ mol^?1 O₃ h^?1, depending on the operating conditions. In the oxidation experiments using oxidants other than ozone, the rate constants varied between 0.06 and 1.19 h^?1. Copyright © 2004 Society of Chemical Industry     

Decomposition of Detergents in Industrial Wastewater by AOP in Flow Systems

The present studies covered investigations of advanced oxidation of detergents in industrial wastewater with the use of ozone, hydrogen peroxide, UV and ionizing radiation separately and in combinations: O₃+UV, UV+H₂O₂, H₂O₂+O₃, O₃+H₂O₂+UV, O₃+ ionizing radiation in the flow systems taking into account specific features of subsequent versions. The aim of these studies was to present results of detergent decomposition in the applied versions and also in the flow systems compared to stationary systems. The radiation processes were carried out with high efficiency in all stationary and flow systems tested. The best results of detergent decomposition were achieved in the samples exposed to simultaneous radiation and ozonation.     

Comparison of Ozone and Hydroxyl Radical-Induced Oxidation of Chlorinated Hydrocarbons in Water

The efficiency of ozonation and advanced oxidation processes such as ozone/UV, ozone/H₂O₂ and H₂O₂/UV was assessed for chlorinated hydrocarbons using a closed batch-type system. 1,1-Dichloropropene (DCPE), trichloroethylene (TCE), 1-chloropentane (CPA), and 1,2-dichloroethane (DCA) were used as model compounds.

The direct reaction between substrates and ozone predominated at lower pH, which resulted in the efficient oxidation of the olefin, DCPE. At higher pH, ozonation resulted in more efficient oxidation of the chlorinated alkanes, with a corresponding decrease in the efficiency of DCPE oxidation. Consistent results were observed for ozone/H₂O₂ and ozone/UV treatment. Due to slow UV-induced decomposition of H₂O₂, the process using H₂O₂/UV (254 nm) resulted in very slow oxidation of all four compounds.

The total ozone requirement to achieve a given degree of elimination (to 37% of the original concentration), δ0.37, was used to assess the combined effects of the direct and indirect reactions for different types of waters.     

Advanced Oxidation of Tannic Acid in Aqueous Solution

Decomposition of tannic acid in aqueous solution in advanced oxidation processes has been studied. Different oxidizing agents: ozone, hydrogen peroxide and UV radiation have been used both as single and mutually combined components of the system. The course of reaction was examined by the changes of chemical oxygen demand (COD) and total organic carbon (TOC) in aqueous solutions. Particular attention has been paid to determine optimal concentration of hydrogen peroxide, when it is used alone, together with O₃ and in H₂O₂+O₃+UV combination. The most effective optimal concentration of H₂O₂ was found. The entire mineralization of tannic acid into final products CO₂ and H₂O can be accomplished in all combinations of advanced oxidation with ozone. Bacteriological test ToxAlert® with luminescence bacteria Vibro fisheri proved that toxicity of solutions decreased considerably during advanced oxidation of tannic acid solution.     

Impact of chemical oxidation on biological treatment of a primary municipal wastewater. 1. Effects on cod and biodegradability

Municipal wastewaters taken from a primary sedimentation tank were subjected to different chemical oxidation processes (ozonation or UV radiation alone or combined with hydrogen peroxide) to observe the evolution of COD and BOD/COD ratios. Ozonation of wastewater led to different increases of COD level reduction depending on pH and carbonate‐bicarbonate ion concentrations. Direct photolysis or hydrogen peroxide alone were found to be inappropriate technologies. On the other hand, advanced chemical oxidation, that is, oxidation with ozone or UV radiation combined with hydrogen peroxide, increased COD level reduction only when wastewater was previously decarbonated. Thus, elimination of carbonate‐bicarbonate ions, increase of pH and addition of hydrogen peroxide (10^‐3 M) yield increases COD level reduction rates. Finally, preozonation also allows improvement of wastewater biodegradability.     

ELIMINATION OF BENZENE AND CHLOROBENZENES BY PHOTODEGRADATION AND OZONATION PROCESSES

Benzene (B) and two representative chlorobenzenes (1,4-dichlorobenzene (DCB) and 1,2,3-trichlorobenzene (TCB)) were oxidized by means of UV irradiation alone, ozone alone, and the combinations UV/H₂O₂ and O₃/H₂O₂. In the single photolytic process, the influence on the photodegradation of the pH, temperature, and type of radiation source used was established. A kinetic study was performed by evaluating the first-order rate constants and the quantum yields. The effect of the additional presence of hydrogen peroxide was pointed out in the combined process UV/H₂O₂,with the determination of the specific contribution of the radical pathway to the overall photodegradation system. In the oxidation by ozone based systems (ozone alone and the combination O₃/H₂O₂), the rate constants at 20°C for the reaction of each compound with ozone and hydroxyl radicals were determined.     

Decomposition of hydrogen peroxide in the presence of activated carbons with different characteristics

BACKGROUND: Catalytic ozonation promoted by activated carbon is a promising advanced oxidation process used in water treatment. Hydrogen peroxide generated as a by‐product from the reaction of ozone with some surface groups on the activated carbon or from the oxidation of some organic compounds present in the water being treated seems to play a key role in the catalytic ozonation process. Hydrogen peroxide decomposition promoted by two granular activated carbons (GAC) of different characteristics (Hydraffin P110 and Chemviron SSP‐4) has been studied in a batch reactor. The operating variables investigated were the stirring speed, temperature, pH and particle size. Also, the influence of metals on the GAC surface, that can catalyze hydrogen peroxide decomposition, was observed. RESULTS: Chemviron SSP‐4 showed a higher activity to decompose hydrogen peroxide than HydraffinP110 (70 and 50% of hydrogen peroxide removed after 2 h process, respectively). Regardless of the activated carbon used, hydrogen peroxide decomposition was clearly controlled by the mass transfer, although temperature and pH conditions exerted a remarkable influence on the process. Catalytic ozonation in the presence of activated carbon and hydrogen peroxide greatly improved the mineralization of oxalic acid (a very recalcitrant target compound). About 70% TOC (total organic carbon) depletion was observed after 1 h reaction in this combined system, much higher than the mineralization achieved by the single processes used. CONCLUSIONS: Of the two activated carbons studied, Chemviron SSP‐4 with an acidic nature presented a higher activity to decompose hydrogen peroxide. However the influence of the operating variables was quite similar in both cases. Experiments carried out in the presence of tert‐butanol confirmed the appearance of radical species. A kinetic study indicated that the process was controlled by the internal mass transfer and the chemical reaction on the surface of the activated carbon. The catalytic activity of hydrogen peroxide in oxalic acid ozonation promoted by activated carbon (O₃/AC/H₂O₂) was also studied. The results revealed the synergetic activity of the system O₃/AC/H₂O₂ to remove oxalic acid. Copyright © 2010 Society of Chemical Industry     

Performance evaluation of ozonation and an ozone/hydrogen peroxide process toward development of a new sewage treatment process—Focusing on organic compounds and emerging contaminants

Performance of ozonation and an ozone/hydrogen peroxide process under a new concept centering on ozonation and/or ozone/hydrogen peroxide processes in sewage treatment processes comprising only physical and chemical processes are discussed, with focus on the removal of matrix organic compounds and emerging contaminants. Matrix organic compounds of filtrated primary sewage effluents were removed to as low as 3.2 mgC/L in the ozone/hydrogen peroxide process at an ozone consumption of around 400 mg/L. Linear relationships between ozone consumption and removal amounts of organic compounds were observed, in which the amounts of ozone required to remove 1 mg of organic carbon were 9.5 and 8.3 mg (2.4 and 2.1 mol-O₃/mol-C) in ozonation and the ozone/hydrogen peroxide process, respectively. Ratios of hydroxyl radical exposure to ozone exposure were in the order of 10^–9 to 10^–8 for ozonation and 10^–7 to 10^–6 for the ozone/hydrogen peroxide process. Experiments and a kinetic evaluation showed that ozonation and/or the ozone/hydrogen peroxide process have high elimination capability for emerging contaminants, even in primary sewage effluent with the thorough removal of matrix organic compounds. Newly found reaction phenomena, the temporal increase and decrease of dissolved ozone and accumulation of hydrogen peroxide in the early stage of oxidation with the continuous feeding of hydrogen peroxide, were presented. Possible reaction mechanisms are also discussed.     

Advanced Oxidation of Textile Wastewaters

Model dyeing and laundering wastewaters produced during two basic technological operations of the textile industry were subjected to treatment by advanced oxidation processes (AOPs). The following agents were used: ozone (O₃), hydrogen peroxide (H₂O₂) and UV radiation. They were applied separately and in all possible combinations: O₃ + UV, O₃ + H₂O₂, UV + H₂O₂, as well as all three at the same time: O₃ + UV + H₂O₂. Effluents before and after the treatment were analyzed according to requirements of the Polish Standards that included pH, color threshold, COD and concentration of anionic and non-ionic surfactants. Ozonation was carried out in a lab-scale bubble column reactor with a centrally located UV burner. The most effective version of AOPs proved to be the simultaneous use of all three agents. In the case of such treatment of dyeing wastewaters nearly complete discoloration and full decomposition of surface-active substances were obtained at 80% reduction of COD. A similar tendency was observed in the case of laundering wastewater, though in that case the results were slightly worse, which may be explained by much higher initial concentrations of the pollutants. Good treatment effects have also been obtained in combined treatment by simultaneous use of hydrogen peroxide and ozone.     

Aqueous degradation of atrazine and some of its main by-products with ozone/hydrogen peroxide

This laboratory study was designed to investigate the removal of atrazine (ATZ) and its first main by-products, deethylatrazine (DEA) and deisopropylatrazine (DIA) by O₃/H₂O₂. At least 76% of the oxidation rate of atrazine is due to free radical reactions. At neutral pH and 20°C, an initial hydrogen peroxide concentration of 10⁻³ M is optimum to reach a maximum oxidation rate of these compounds. Experimental results of oxidation in the presence of high hydrogen peroxide concentrations allow the mass transfer coefficient of ozonation to be determined. This coefficient, reactor flow analysis and kinetic data obtained have been applied to mol balance equations of atrazine, deisopropylatrazine, deethylatrazine, ozone (both in the gas and water) and hydrogen peroxide to obtain their corresponding concentrations at different conditions. © 1998 SCI     

The Combination of Ozone/Hydrogen Peroxide and Ozone/UV Radiation for Reduction of Trihalomethane Formation Potential in Surface Water

Applied ozone dosages of 20, 25, and 30 mg/L to lake water utilized by the city of Shreveport, LA produced no significant reductions in trihalomethane formation potentials (THMFP). However, the addition of 20 mg/L of hydrogen peroxide and/or 0.67 W/L of UV radiation (254 nm) in combination with ozone produced decreases in THMFP of over 60% in 60 minutes. Smaller THMFP decreases were seen with shorter contact times. The use of H₂O₂ and/or UV in combination with O₃ increased the percentage of applied ozone consumed by the lake water (i.e., enhanced the ozone mass transfer) five times over simple ozonation.     

Combination of chemical oxidation‐membrane filtration processes for the elimination of phenyl‐ureas in water matrices

BACKGROUND: Phenyl‐urea herbicides are found in surface waters and wastewaters as a consequence of their extensive use in agriculture. Due to their pollutant power, the removal of phenyl‐ureas is a priority objective in water treatment technologies. RESULTS: Four selected phenyl‐ureas herbicides (linuron, diuron, chlortoluron and isoproturon), dissolved in two water matrices (a groundwater and and a reservoir water), were subjected to sequential combinations of chemical treatments and membrane filtration processes. Two specific sequences were conducted: first, a chemical oxidation stage (where UV radiation, ozone and ozone plus hydrogen peroxide were used) followed by a nanofiltration process; and second, a membrane filtration stage (using UF and NF membranes) followed by an ozonation stage. Values for the herbicide removals in the oxidation stages and for the rejection coefficients in the filtration stages are provided, and the partial contribution of the different stages is established for each combined treatment. CONCLUSIONS: High removals (over 80%) were reached for phenyl‐ureas elimination by most of the combined processes tested. In the combined chemical oxidation/nanofiltration processes, the most effective was an ozonation pretreatment ([O₃]₀ = 1.5 mg L^?1)) followed by a NF step. In the opposite sequence filtration/chemical oxidation, the most effective was a NF pretreatment followed by the ozonation ([O₃]₀ = 2 mg L^?1). Copyright © 2009 Society of Chemical Industry     

Oxidation of Esculetin,a Model Pollutant Present in Cork Processing Wastewaters,by Chemical Methods

The ozonation of esculetin (6,7-dihydroxycoumarin), a major pollutant present in the wastewater generated in the cork industry, was accelerated at high pH, with apparent second-order rate constants in the range from 3.3 × 10⁴ L/(mol·s) at pH=2 to 8.4 × 10⁷ L/(mol·s) at pH=9. The acid-base equilibrium of esculetin was studied, resulting in a pK_a value of 7.37. Taking into account this pK_a, the rate constants for the reaction between ozone and the un dissociated and dissociated forms of esculetin were 3.0 × 10⁴ and L/(mol·s) 6.67 × 10⁸ L/(mol·s), respectively. Apparent first-order rate constants for the photolysis by UV irradiation were also evaluated, with values between 0.12 × 10^?2 min^?1 at pH=2 and 1.15 × 10^?2 min^?1 at pH=9, while the quantum yields for this photo-degradation reaction varied from 0.99 × 10^?2 mol/Eins to 11.1 × 10^?2 mol/Eins at these pHs. The Fenton's reagent system was used for the generation of hydroxyl radicals, and the rate constant for the reaction between esculetin and these radicals was determined to be 1.06 × 10¹⁰ L/(mol·s). Finally, several chemical oxidation systems were used in the degradation of this pollutant: single oxidants (ozone, UV irradiation) and advanced oxidation processes (Fenton's reagent, UV/H₂O₂, O₃/H₂O₂, O₃/UV, O₃/H₂O₂ /UV, and photo-Fenton system). The results revealed that the most efficient methods in terms of esculetin removal were ozonation among the single oxidants, and the photo-Fenton system among the combined processes.     

Bromate Formation in Ozone and Advanced Oxidation Processes

Both the direct ozone reaction and the indirect hydroxyl radical reaction are important in ozonation of drinking water. This article investigates the effectiveness of ozone versus the advanced oxidation process of ozone coupled with hydrogen peroxide in the formation of bromate. The investigation was conducted on a pilot scale at various H₂O₂:O₃ dose ratios of 0.1, 0.2, and 0.35 at different times of the year. The results of this study show a reduction in bromate with the addition of hydrogen peroxide to an ozone system versus ozone alone. It was also observed that bromate increased with increased H₂O₂:O₃ ratios; however, concentrations were still lower than those in the ozone only system.     

Ozonation And AOP Treatment Of Phenanthrene In Aqueous Solutions

Phenanthrene is considered to be a hazardous pollutant and is listed as a priority pollutant by the U.S. EPA. This laboratory study was designed to investigate the degradation of phenanthrene in water solutions by ozone, by ozone in combination with hydrogen peroxide and UV-radiation and by UV-radiation only, to compare the efficiency of different oxidation processes at different values of pH = 3, 7 and 9. On the basis of kinetic curves of phenanthrene destruction, the chemical reaction rate constants were calculated. The results obtained confirmed that phenanthrene oxidation proceeds mostly with molecular ozone and the best method for reducing its concentrations is an ozonation in neutral medium. The rate of phenanthrene autoxidation is rather slow and does not depend on pH nor H₂O₂ addition. UV-radiation alone is also unable to reduce phenanthrene concentration significantly.     

The Effect Of Preozonation,Ozone/Hydrogen Peroxide Treatment,And Nanofiltration On The Removal Of Organic Matter From Drinking Water

Pilot scale experiments were performed to evaluate the ability of ozonation, ozone/hydrogen peroxide treatment and nanofiltration to reduce levels of organic matter, mutagenicity, total adsorbable halogens, color and turbidity from purified and bank-filtered surface water rich with humic material.

Ozonation and ozone/hydrogen peroxide decreased the amount of organic material from drinking water by about 20 percent measured as TOC and COD_Mn. Color and turbidity level reductions were 49 and 11 percent, respectively. Ozonation reduced the AOX concentrations formed during postchlorination from 150 μgL^?1 to 75 μgL^?1. The addition of hydrogen peroxide further improved the removal to 37 and 26 μgL^?1 depending on the ratio of H₂O₂/O₃. The mutagenicity reduction followed the same pattern: without ozonation the chlorination-derived mutagenicity was 1,450 net revertant L^?1 after the ozonation 700 and after the H₂O₂/O₃ treatment from <100 to 400 net revertant L^?1 depending on the H₂O₂/O₃ ratio. Nanofiltration appeared to be the most effective way to remove organic material. The removal of TOC was 68%, COD_M 72%, color 90%, turbidity 68%, AOX 88%, and mutagenicity 85%.