Cost Effectiveness of Ozonation and AOPs for Aromatic Compound Removal from Water: A Preliminary Study

The capital and operating costs for several aromatic compounds (phenanthrene, 2,4-dimethylphenol, 2,4,6-trichlorophenol, nitrobenzene) removal from polluted groundwater using ozonation and advanced oxidation have been estimated on the basis of the laboratory experiments in semibatch conditions. The pollutants initial concentration was in the range of 0.01–1.0 mM. In the calculations the polluted groundwater flow rate was taken 40 m³/h with the initial pH = 7.0. It is shown that polluted groundwater purification from the aromatic pollutants with the initial concentration in the range of 0.01–1.0 mM using ozonation and advanced oxidation is economically feasible.     

Ozonation of Sulfur-Containing Aliphatic Compounds in Aqueous Solution. I

In view of the possible reaction of ozone with sulfur containing natural and anthropogenic compounds, the oxidation products of sulfur-containing aliphatic model compounds in pure water in dependence on pH value were investigated.

In the first part, as a model compound for thioether, thiodiglycolic acid was investigated. The rate of elimination is independent of pH-value. At pH 3 as primary product thionyldiglycolic acid is formed, which undergoes further oxidation, but very slowly, to sulfonediacetic acid, which is very stable against ozone attack at pH 3. At pH 7 and higher, however, thionyldiglycolic acid is oxidized faster to sulfonediacetic acid, and this compound is oxidized to sulfoacetic acid, oxalic acid, glyoxylic acid, sulfateion, and CO₂ after longer reaction times. In all cases, sulfite as an inorganic intermediate product could not be identified. Also the intermediate products in pure solutions are ozonized. The mass balances show that 90 to 95% of the oxidation products could be identified. Based on these results, reaction schemes are discussed.     

Kinetic Description of Industrial Wastewater Ozonation Processes

Literary and experimental data on the ozonation kinetics of aqueous solutions and wastewater were analyzed. COD was suggested to be used as a kinetic parameter from the solution side. On the basis of the results obtained from the ozonation of model solutions and wastewater, the rate coefficient by COD of the reaction was shown to be constant during separate stages of the process. Due to the consumption of fast-reacting components and entering into the reaction of more slowly reacting intermediate products, the rate coefficient changed spasmodically with transition from one stage to another. The reaction order with respect to the COD of the solution was shown to be equal to the reaction order with respect to the pure component.     

The pH Dependence and Effects of the Oxidative Products of Some Aromatic Compounds in Ozonation under Irradiation

Some aromatic compounds (o–nitrotoluene, p–nitrotoluene–2–sulfonic acid, and p–medthylaniline–3–sulfonic acid), were ozonized under UV irradiation separately, and the oxidative efficiencies of these reactions were studied. In order to ensure continued oxidation, it is advantageous to choose a proper pH value so as to fit the requirements of the chain reaction and also diminish the amound of HO. scavengers such as CO₃ ⁼ and HCO₃ ^? in oxidation Products. Removal of carbon dioxide could be effected by acidification of the reaction mixture. In order to decrease the inhibiting effect of the oxidation products, it is advisable to vary the pH value at different stages of UV ozonation. Many refractory organics usually encountered in industrial wastewater may resist degradative oxdation by ozonation alone, but can be destroyed rapidly by UV–radiation combined with ozonation.     

Aqueous Ozonation of Pesticides: A Review

The ozonation reactions of pesticides in aqueous solution have been reviewed. Degree of reaction and reaction product identity are included. Compounds are classified into five groups: chlorinated hydrocarbons, organophosphorus compounds, phenoxyalkyl acid derivatives, organonitrogen compounds, and phenolic compounds. Experimental conditions for each study are summarized. Much work has been carried out under conditions atypical of those encountered at drinking water treatment plants. Thus, the findings of the papers reviewed cannot be applied directly to potable water treatment.     

The Potential Use of Ozone and Peroxidase for Removal of Aromatic Compounds from Water by Polymerization

Oxidation organics by ozone has been the object of extensive studies. A great number of these concern the aromatic ring cleavage, but polymerization by ozone or enzyme, such as peroxidase, was not greatly studied. In this paper, the effects of ozone or enzyme on the polymerization of dichlorophenol, under the conditions of potable water treatment are studied using HPLC, scintillation counting, exclusion chromotography, and GC-MS. These techniques permit the characterization and identification of polymers.Even at low concentrations these compounds may cause taste and odor problems, or represent a health risk based on toxic and mutagenic considerations.     

Ozonation of Aqueous Solutions of Nitrogen Heterocyclic Compounds : Benzotriazoles,Atrazine and Amitrole

Study of the ozonation of aqueous solutions of four heterocyclic nitrogen compounds, at slightly acidic pH in a heterogeneous gas-liquid system, showed that the reactivities of these compounds are different. Amitrole, a five-membered ring heterocycle, has been found to be a highly reactive compound, while atrazine, a six-membered ring heterocycle, has been found to be a poorly reactive compound. The benzotriazoles, benz-fused five-membered ring heterocycles, present intermediate reactivities. Moreovoer, the chemical natures of the ozonation by-products have been found to be different between amitrole and atrazine. With atrazine, ozone did not open the heterocyclic ring, and led to the formation of a trioxotriazine. With amitrole, ozone broke the heterocyclic ring and formed mainly formamide.     

Perovskite Catalytic Ozonation of Some Pharmaceutical Compounds in Water

The ozonation of two pharmaceutical compounds: the drug diclofenac (DCF) and the synthetic hormone 17α-ethynylstradiol (EST), has been studied in laboratory prepared water and domestic wastewater in the presence of perovskite catalysts. In ultrapure water, catalysts do not lead to any improvement on the ozonation rates of DCF and EST which supports the fact that both compounds are removed by direct ozonation. TOC removal, on the other hand, is significantly increased in the presence of perovskite catalysts, especially when copper perovskite is used, with TOC removals in the order of 90% after 120 minutes of reaction. In domestic wastewater the results are similar regarding the mechanism of initial pharmaceutical compounds removal, which are due to direct reactions with ozone that, in this case, develop during longer reaction times likely due to the presence of other contaminants. Then, regarding TOC removal in domestic wastewater, negligible differences between non-catalytic and catalytic ozonation are observed during the first approximately 25 minutes of reaction. For higher reaction time, TOC removal is improved only in the case copper perovskite catalyst is used although percentages of TOC removal are comparatively lower than those reached in ultrapure water (they hardly reach 50% TOC removal). Finally, a kinetic study has been carried out and apparent rate constants of the heterogeneous reaction between ozone and TOC on the catalyst surface have been determined.     

Removal Characteristics of Organic Pollutants in Sewage Treatment by a Pre-Coagulation,Ozonation and Ozone/Hydrogen Peroxide Process

The applicability of a sequential process of ozonation and ozone/hydrogen peroxide process for the removal of soluble organic compounds from a pre-coagulated municipal sewage was examined. 6–25% of initial T-COD_Cr was removed at the early stage of ozonation before the ratio of consumed ozone to removed T-COD_Cr dramatically increased. Until dissolved ozone was detected, 0.3 mgO₃/mgTOC₀ (Initial TOC) of ozone was consumed. When an ozone/hydrogen peroxide process was applied, additional COD_Cr was removed. And we elucidated that two following findings are important for the better performance of ozone/hydrogen peroxide process; those are to remove readily reactive organic compounds with ozone before the application of ozone/hydrogen peroxide process and to avoid the excess addition of hydrogen peroxide. Based on these two findings, we proposed a sequential process of ozonation and multi-stage ozone/hydrogen peroxide process and the appropriate addition of hydrogen peroxide. T-COD_Cr, TOC and ATU-BOD₅ were reduced to less than 7 mg/L, 6 mgC/L and 5 mg/L, respectively after total treatment time of 79 min. Furthermore, we discussed the transformation of organic compounds and the removal of organic compounds. The removal amount of COD_Cr and UV₂₅₄ had good linear relationship until the removal amounts of COD_Cr and UV₂₅₄ were 30 mg/L and 0.11 cm^?1, respectively. Therefore UV₂₅₄ would be useful for an indicator for COD_Cr removal at the beginning of the treatment. The accumulation of carboxylic acids (formic acid, acetic acid and oxalic acid) was observed. The ratio of carbon concentration of carboxylic acids to TOC remaining was getting higher and reached around 0.5 finally. Removal of TOC was observed with the accumulation of carboxylic acids. When unknown organic compounds (organic compounds except for carboxylic acids) were oxidized, 70% was apparently removed as carbon dioxide and 30% was accumulated as carboxylic acids. A portion of biodegradable organic compounds to whole organic compounds was enhanced as shown by the increase ratio of BOD/COD_Cr.     

Effect of Ozonation on the Chlorine Demand of a Treated Surface Water and Some Macromolecular Compounds

The study described in this paper was conducted to examine the effects of ozonation and ozone-GAC filtration treatment steps on chlorine consumption of the Seine river water treated in the Choisy-le-Roi drinking water works. Ozone-GAC combined treatment was found to significantly reduce both the initial chlorine demand and the long-term chlorine demand of waters, excepting for waters sampled during cold months of the year. The removal of the chlorine demand potential by ozonation alone was found to be limited for the studied waters and for solutions of macromolecular compounds even in the presence of carbonate species. Ozonation carried out in the absence of bicarbonate ion was found to increase reactive sites with chlorine treatment of an aquatic fulvic extracted from the Seine river water.     

Quinoxaline Ozonation in Aqueous Solution

The oxidation of quinoxaline by ozone in aqueous solution is investigated. The chemical and kinetic evolution of the oxidation process at varying pH are followed by means of semi-batch and batch ozonation experiments. Results indicate that quinoxaline ozonation can develop according to both radical and ionic mechanisms whose relative occurrence can be varied by means of addition to the reacting system of radical scavengers or ozone decomposition promoters. It is shown that each mechanism involves an initial attack of ozone to both the homocyclic and heterocyclic rings of quinoxaline. Pyrazinedicarboxylic acid is formed as a stable final product in ionic ozonation, whereas it appears as an intermediate still reactive towards ozone in radical ozonation. Despite this, the radical ozonation of quinoxaline appears to be more selective than ionic zonation with respect to production of pyrazinedicarboxylic acid. Reaction schemes are proposed to account for the observed kinetic behaviors and product formations.

Oxidation experiments have also been extended to pyrazine, and its sensitivity to only radical ozonation is shown.     

Ozonation Of Sulfur-Containing Aliphatic Compounds In Aqueous Solutions. II. Cysteine,Cystine and Thioglycolic Acid

In view of the possible reaction of ozone with sulfur-containing natural and anthropogenic compounds, the ozonation of cysteine, cystine, thioglycolic acid and their oxidation products at pH 3 and 7 (initial concentration 1 mmol/L) was investigated. The oxidation of cysteine at pH 3 leads to cysteic acid; at pH 7 sulfoacetic acid, sulfate, ammonia and nitrate are formed besides cysteic acid. Cysteinesulfinic acid as intermediate oxidation product was not identified because of the very fast reaction with ozone forming cysteic acid.     

Aqueous Ozonation Of Fatty Acids

The reactivity of a series of fatty acids toward ozone was examined in aqueous solution at low substrate concentration (μg.L^?1 range). Saturated fatty acids were unreactive, unsaturated fatty acids were readily consumed. A number of reaction products or their methylated derivatives were identified by gas chromatography and gas chromatography-mass spectrometry. The products identified are consistent with a 1,3-dipolar cyclo-addotion reaction.     

Catalytic Ozonation of Gasoline Compounds in Model and Natural Water in the Presence of Perfluorinated Alumina Bonded Phases

Gasoline compounds are one of the most widespread causes of soil and groundwater contamination. Their degradation in model and natural waters due to catalytic ozonation in the presence of perfluorooctylalumina (PFOA) is presented and discussed in this paper. The results obtained clearly indicate that the PFOA/O₃ system is effective mainly for ether (MTBE and ETBE) removal from both model and natural water. The catalytic activity of PFOA is not so significant in the case of BTEX ozonation. An investigation into by-product formation has shown that the concentration of both carboxylic acids (mainly oxalic acid) and carbonyl compounds (mainly acetone) increases after catalytic ozonation when compared with ozonation alone. A decrease of formic acid and formaldehyde takes place after the PFOA/O₃ system as opposed to the usage of ozonation alone.     

Pyruvic Acid Removal from Water by the Simultaneous Action of Ozone and Activated Carbon

Activated carbon (AC) has been used to catalyze the ozonation of pyruvic acid in water. Pyruvic acid conversions were found to be 9 and 37% after 90 min of single ozonation and single adsorption with 40 gL^?1 AC, respectively, while 82% was reached at the same conditions during the AC catalytic ozonation. Also, for similar conditions, mineralization reached values of 67% in the AC catalytic ozonation against hardly 5% in the non-catalytic experiment. The process likely develops through both adsorption of ozone and pyruvic acid on the AC surface and generation of hydroxyl radicals that eventually is the responsible oxidizing species. Rate constants for both non-catalytic ozonation and AC-Ozone catalytic surface reaction, at 20°C and pH 7.5, were found to be 0.025 min^?1 and 87.9 Lg^?1s^?1, respectively. For AC concentrations higher than 2.5 gL^?1 gas-liquid mass transfer of ozone constituted the limiting step. At lower concentrations, internal diffusion plus surface reaction controlled the process rate.     

Advanced Oxidation Treatment of Drinking Water: Part I. Occurrence and Removal of Pharmaceuticals and Endocrine-Disrupting Compounds from Lake Huron Water

The current study focuses on the occurrence of selected endocrine disrupting compounds, pharmaceuticals and personal care products in Lake Huron Water and their removal using ozone/hydrogen peroxide based pre-coagulation, advanced oxidation process (AOP). Raw Lake Huron water spiked with nine target compounds was treated in a dual train pilot scale treatment plant. None of the target chemicals showed any significant removals following conventional treatment processes (coagulation, sedimentation and filtration). Five of the nine target pollutants plummeted to concentrations below the method detection limits following AOP. For all the target compounds AOP treatment provided higher removal compared to conventional treatment.     

Preliminary Results on Ozonation Enhancement by a Perfluorinated Bonded Alumina Phase

A preliminary study was undertaken in order to determine the efficiency of ozonation in the presence of perfluorooctylalumina (PFOA) for the removal of organic substances from aqueous solutions by ozone. PFOA was synthesized by reacting hydrated alumina with pentadecafluorooctanoic acid. A monomolecular layer of non-polar perfluorinated alkyl chains, orientated away from the surface of alumina, capable of dissolving ozone and organic molecules, was obtained. The efficiency of ozonation alone and ozonation in the presence of PFOA or Al₂O₃ was compared. PFOA was found to significantly enhance the degradation level of organic substances in comparison with ozonation alone. Al₂O₃ did not show any catalytic activity.     

Cellular Toxicity and Mutagenicity Assays from On-Site Sampling of Drinking Water Treatment Plants Using Multistage Ozonation

Studies were carried out on-site in a potable water production plant utilizing ozonation treatment at three stages of the process. The quality of water in the treatment line was studied by chemical analysis, but also for toxicity to Hela cells after XAD resin concentration, and for mutagenesis to Salmonella Ames strains and mammalian cells V79 HGPRT system. With a sufficient dose of ozone and activated carbon adsorption, the initial cytotoxicity of the raw water and the mutagenic or promoter activity are destroyed.     

Ozonation of Polycyclic Aromatic Hydrocarbons in Water Solution

The degradation of three polycyclic aromatic hydrocarbons (PAHs): benzo[a]pyrene (BAP), chrysene (CHR), and fluorene (FLU) in aqueous solution using ozone was investigated. The influence of pH of the reaction mixture, ozone concentration, and the presence of a radical scavenger on the reaction rate was determined. The highest rate of PAHs disappearance was achieved in acidic solutions. The radical scavenger, tert-butanol, effectively inhibited the rate of PAHs destruction. The rate constants of direct reaction of PAHs with ozone were calculated and they were equal to (3.32 ± 0.21) × 10⁴; (1.10 ± 0.15) × 10⁴ and 44.8 ± 1.1 M^?1s^?1 for BAP, CHR, and FLU, respectively. The contributions of direct ozonolysis, and radical reaction to PAHs oxidation in ozonation processes, were evaluated.     

Degradation of Refractory Organic Pollutants by Catalytic Ozonation—Activated Carbon and Mn-Loaded Activated Carbon as Catalysts

A novel catalyst for the ozonation process was prepared by loading manganese on the granular activated carbon (GAC). Nitrobenzene was used as a model refractory organic micropollutant in this study. The catalytic activity of GAC and the Mn-loaded GAC were studied respectively. The removal efficiency of nitrobenzene by Mn-loaded GAC catalyzed ozonation could reach 34.2–49.9%, with the oxidation efficiency being about 1.5–2.0 times higher than that achieved in GAC catalyzed ozonation and 2.0–3.0 times higher than that achieved by ozonation alone. The effect of pH and the t -butanol on the GAC/ozone process was discussed. The optimum condition for preparing the catalyst was studied.