Formation Of Aldehydes During Ozonation

This study investigated the formation of aldehydes after ozonation of three real and three model waters reconstituted from hydrophobic organic material. The four main aldehyde species formaldehyde, acetaldehyde, glyoxal, and methyl glyoxal were analyzed. Formaldehyde was the dominant species formed as a result of ozonation. The different waters varied greatly with respect to aldehyde production under similar treatment conditions. Studies conducted with model waters allowed for exploring aldehyde formation as a function of various water quality parameters. Overall, the hydrophobic organic extracts appeared to have greater aldehyde formation potential than the hydrophilic organics. Aldehydes were formed in direct proportion to the total organic carbon (TOC) concentration of the water at a 1:1 ozone-to-TOC ratio. Greater aldehyde formation was observed at lower ozonation pH values. Bromide ion and inorganic carbon added to model waters appeared to have no effect on aldehyde production. Finally, Assimilable Organic Carbon (AOC) measurements exhibited a strong correlation between aldehyde production and AOC production.     

Rationales for Multiple Stage Ozonation in Drinking Water Treatment Plants

Starting in the early 1970s, the application of ozone for drinking water treatment began to evolve from primarily single-purpose, single-stage use for disinfection, taste and odor control or iron and manganese oxidation, to multipurpose uses of ozone. As a result, most of the newer drinking water treatment plants have installed two- and even three-stages of ozonation. in order to maximize the technological benefits of ozone and to minimize the costs involved.     

Ozonation of Drinking Water: A Design Methodology

The formation of potentially carcinogenic organic halides has been shown to result from drinking water disinfection with chlorine. xidative treatment of organic halide precursors with ozone prior to chlorination has surfaced as an attractive technique for reducing the formation of these compounds. In addition to reduction of precursor levels, preozonation has been reported to effect other beneficial results in water treatment. This paper presents design methodologies to optimize the implementation of the ozonation process for water treatment applications. Pre-design considerations common to all ozonation design processes are discussed. Subsequently, design procedures for the ozone generation and contacting systems are reviewed.     

Study of the Catalytic Ozonation of Humic Substances in Water and Their Ozonation Byproducts

It is shown that using transition metals, especially Mn(II) and Ag(I), during ozonation of humic substances in water allows important reductions in the content of organic matter. Characterization of the organic compounds resulting from ozonation was made by concentrating the sample through liquid-liquid extraction or derivation with PFBOA.HCl, along with the GC/MS and GC/ECD techniques. In total, 110 different organic compounds were identified using GC/MS; mainly carboxylic acids, aromatics, hydrocarbons, aldehydes, ketones, and furan-carboxylic acids. The percentages of elimination or formation levels reached during ozonation are discussed.     

Bromate Formation during Ozonation of Bromide Containing Drinking Water- a Pilot Scale Study

The effect of bromide ion concentration, pH, temperature, alkalinity, and hydrogen peroxide content on bromate formation was studied. Increase in pH was found to give the greatest increase in bromate formation. Also increase in the ozonation temperature, bromide ion concentration and hydrogen peroxide content increased the observed bromate concentration. Only increased alkalinity decreased the bromate formation during the ozonation experiments. Bromate formation exceeded the EU limit value for bromate ion, 10 μg/l, when the initial bromide ion concentration was around 100 μg/l, except for the alkalinity of 1.4 mmol/1, when the bromate formation was 9.4 μg/l.     

Ozonation Enhancement with Nonpolar Bonded Alumina Phases

This article presents the results obtained for humic acid (HA) degradation in drinking water by means of an ozonation process in the presence of a nonpolar bonded alumina phase. It was observed that (perflurooctylalumina) (PFOA) is characterized by its high adsorption capacity toward HA. The adsorption properties of bare alumina and alumina modified with perfluorooctanoic acid appeared to differ significantly toward the various organic substances examined. The ozonation process carried out in the presence of PFOA was found to be more efficient for the removal of HA from water than the other two examined ozonation systems: ozonation alone and ozonation in the presence of bare alumina; however, a catalytic activity of bare alumina cannot be denied. The effect of by-products formation and changes in the molecular size distribution of HA were studied in the case of all three examined ozonation systems. The influence of catalyst dosage and ozonation time was also investigated.     

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.     

Fifteen Years Experience In Ozonation For Drinking Water In Montreal

Since 1978, the City of Montreal has been operating an ozonation facility at one of its two water filtration plants. Various studies have been conducted which have resulted in improvements to the process. Among these projects, evaluation of THMs and haloacetic acids, optimization of the dryers' regeneration cycle, evaluation of the ozone recirculation system, revision of the ozone generators' cleaning program and implementation of ozonation process control loops have been undertaken. The reliability of the ozone plant has now been proved with downtimes less than 1% for the past six years.     

Effects Of Catalysts During Ozonation Of Salicylic Acid,Peptides And Humic Substances In Aqueous Solution

The oxidation of two model molecules (salicylic acid and a peptide) and humic substances in aqueous solution was studied using ozone in the presence of various catalysts. Experiments were performed in reactors operated either in batch (TOC_o = 2.5 mg C.L^?1) or in semi-continuous flow mode (TOC_o = 42 mg C.L^?1).     

Formation of Ketoacids in Ozonated Drinking Water

Three ketoacids; glyoxylic acid, pyruvic acid and ketomalonic acid, were identified in ozonated drinking waters and fulvic acid solutions using gas chromatography-mass spectrometry. It was found that the concentrations of ketoacids were much higher than those of aldehydes in ozonated waters. The significance of ketoacids in finished drinking waters is discussed.     

Destruction of Volatile Organic Contaminants in Drinking Water by Ozone Treatment

Controlled, pilot-plant ozone treatment tests were conducted on twenty-nine volatile organic contaminants in distilled water and groundwater. Results show that aromatic compounds and alkenes are well removed by ozone treatment, but that alkanes are poorly removed. Also, efficiency of destruction improved for the alkenes and aromatic compounds with increasing applied ozone dosage and, for some alkanes, with increasing pH. For most compounds, the efficacy of ozone was not severely affected by the background water matrix. Generally, information gathered from the literature regarding rate constants for the ozone treatment of compounds in the gaseous phase or in organic solution predicted, to a useful degree, the effectiveness of ozone in treating aqueous solutions in the present study.

Several of the test conditions selected for this preliminary study may be similar to those found in drinking water treatment plants. Consequently the findings of this research may help guide utilities in their choice of alternative treatments to meet Maximum Contaminant Levels for volatile organic contaminants such as trichloroethylene and benzene.     

Ozonation/Post-Chlorination of Humic Acid: A Model for Predicting Drinking Water Disinfection By-Products

Experiments were performed to evaluate disinfection by-products in model humic acid solutions which were ozonated at three different ozone to carbon levels and then chlorinated. These experiments were conducted in order to help understand whether the ozone/post-chlorination process alters the amount and type of mutagenic by-products formed, from those produced by chlorination of humic acid alone. Disinfection by-products were identified by gas chromatography/mass spectrometry (GC/MS). Samples of clarified and sand-filtered Mississippi River water at a pilotscale drinking water treatment plant in Jefferson Parish, Louisiana, that were ozonated and post-disinfected with chlorine, also were analyzed by GC/MS. A comparison of the by-products in the pilot plant study versus those in our laboratory study showed that similar compounds were produced. The effect of bromide ion in the pilot plant water on by-product formation also is discussed.     

Aqueous Ozonation Of Surfactants: A Review

The aqueous ozonation reactions of surfactants have been reviewed, including the degree of reaction and ozonation byproduct identity. Compounds are classified into three groups: anionic, cationic and non-ionic surfactants. Experimental conditions for each study reviewed are summarized. Much work has been carried out under conditions unlikely to occur during drinking water treatment. Thus, most of the findings of the papers reviewed cannot be directly applied to potable water treatment. However this review can serve to indicate the likely reactivity of the individual surfactants towards ozone and the possible byproducts formed. This reactivity depends mainly upon the chemical structure of the surfactants. The removal of surfactants is pH dependent, with the best results being obtained in alkaline media. High ozone doses usually do not cause complete disruption of the surfactants, while smaller doses are sufficient to enhance their biodegradation.     

The Oxidation of Manganese and Disinfection By Ozonation in Water Purification Processing

The surface water of a river has been used as the raw water by the Waterworks Bureau of Osaka City. At present, the manganese contained in the raw water is oxidized by breakpoint chlorination and all oxides are removed by coagulation, sedimentation followed by rapid sand filtration, with chlorine being used as the final disinfectant.

Prechlorination was not conducted in the ongoing pilotplant experiment of an advanced water purification process with ozone and granular activated carbon. It is necessary, therefore, to oxidize manganese by the oxidative effect of ozone instead of prechlorination.

It is important for the treatment of manganese to adjust the ozone dosage because manganese is oxidized up to the soluble septavalent state by the surplus ozone. Since ozone does not continue to exist for very long in water, though its disinfecting power is high, final disinfection by chlorine is required.     

Ozonation Of Nucleic Acid Constituents

Ozonation of nucleic constituents in pure water in semi-batch reactor, showed that nucleobases and nucleosides behave in a similar way, regarding ozone consumption and inorganic nitrogen formation. Stoichiometric ratios were found about 1 mole of consumed ozone per mole of oxidized nucleobase and nucleoside, except for adenine and adenosine which presented a stoichiometric ratio near 3 moles per mole. Concerning inorganic nitrogen formation, we noted that the presence of primary amino groups induced ammonia and nitrate formations, but never more than one mole per mole of initial compound. Carbon dioxide and other end-products were released during ozonation of adenine and thymine. GC/MS analyses showed the presence of some simple end-products, such as oxalic acid, urea and carbamic acid. However trioxotriazine (or cyanuric acid) seemed to be an important end-product, issued from a cyclic trimerization of formamide followed by oxidation of carbon-nitrogen double bonds.     

Conditions Affecting Bromate Formation During Ozonation of Bottled Water

Bromate concentration, ozone lifetime and ozone exposure (CT value) measured in bottled water in full-scale runs, were in good agreement to those measured in laboratory experiments. Ozone lifetime in bottled water was high enough to result in a CT value greater than 5 even for ozone dose as low as 0.1?mgO₃/L, at a water pH of 7.6. Bromate was gradually formed during the ozone lifetime. Bormate formation and ozone exposure were significantly influenced by pH. In full-scale runs, an ozone dose of 0.15?mgO₃/L at pH=7.6 resulted in a CT of 10.3 and a bromate concentration of 13.5?µg/L, while at pH=7.25 the values of CT and BrO₃ ^? were 12.6 and 9.6?µg/L, respectively. By decreasing further the pH to 6.8, an increase of CT value to 15.8 and a reduction of bromate to 5.5?µg BrO₃ ^?/L were observed. In addition, results in full-scale runs showed that ozone exposure and bromate concentrations were linearly related to ozone dose in the working range of 0.1 to 0.25?mgO₃/L.     

Origin and Conditions of Ketoacid Formation During Ozonation of Natural Organic Matter in Water

The batch ozonation of some fractions of aqueous humic substances (humic, fulvic and hydrophilic acids) extracted from natural waters is studied. The reaction leads to oxidation byproducts such as low molecular aldehydes and ketoacids. Formation conditions and origin of some of them (glyoxylic, pyruvic and ketomalonic acids) regarding the extracted fraction of natural organic matter is established.     

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.     

The Price Of Ozonation In The Paris (France) Suburbs

The purely economic aspects of ozonation have, until now, given rise to surprisingly few publications. Yet they are of ever-growing importance in deciding on the choice of a system, if only because the number of competitive technical solutions available for ozone production has greatly increased.

First of all, an obvious fact must be remembered. Each installation is a special case. It is therefore out of the question to present general results with direct across-the-board applications. On the other hand, it is possible to engineer a general methodology for price calculation and apply it to a few specific examples. As operator of a large number of these facilities, Compagnie Générale des Eaux can present economic results in many, widely different technological economic conditions.

Generally speaking, it can be said that the cost of ozonation is increasingly optimized. This technique, considered a few years ago as a luxury, is now technically and economically ready for incorporation on an equal footing in most treatment trains.