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.     

Formaldehyde Formation During Ozonation Of Drinking Water

Partial oxidation of natural organic material during ozonation produces oxygenated by-products of low molecular weight. Formaldehyde, being the most common oxygenated by-product of ozone, is considered to be a problematic compound by the water industry due to its potential adverse health effects. This research attempts to provide specific information on the effects of water quality parameters, specifically, pH and alkalinity, the structure of humic material, and the operational parameters, e.g., ozone dosage and contact time, on generation of formaldehyde. The results showed that ozonation caused almost an immediate formation of formaldehyde, which reached a peak value, and then started to decrease with continued ozonation. Ozonation of aqueous fulvic acid produced higher concentrations of formaldehyde compared to other types of humic material. Formaldehyde formation was suppressed by high bicarbonate levels, and enhanced at higher pH. Formaldehyde accumulation was more dramatic at low ozone dosages.     

Soil Fulvic Acid Degradation By Ozone In Aqueous Medium

Armadale Armadale soil fulvic acid (SFA) was found to contain several loosely bound organic impurities which could be removed by ethyl acetate extraction. The ozonation of purified Armadale SFA at a variety of dosages was characterized by monitoring the UV absorbance, weight loss, pH changes, total acidity, molecular weight and elemental composition. SFA could only be partially degraded even under ozone dosages as high as SFA/O₃ (w/w) of 1:6. At high ozone dosages (SFA/O3 1:6) mostly aliphatic compounds rich in oxygen were produced, whereas at low ozone dosages (SFA/O₃ < 1:0.5) mainly benzene polycarboxylic acids and polyhydroxy benzene polycarboxylic acids were found. The solid material bisolated from the chlorination (0.5 mg/L residual level) of residues from the ozonation (SFA/O₃ 1:0.2 to 1:0.5) of Contech SFA did not contain any chlorinated products.     

Using Fractionated Natural Organic Matter to Quantitate Organic Byproducts of Ozonation

An improved procedure was used to isolate and fractionate natural organic matter (NOM) in water for subsequent ozonation and disinfection by-product (DBP) and color removal quantisation. Isolated NOM fractions from two different sources, accounting for approximately 50 to 60% of the dissolved organic material and 60 to 75% of the color, were characterized and then ozonated under conditions approximating those encontered during drinking water treatment. The natural waters also were ozonated. Organic DBPs of either health concern or which may contribute to biological instability of finished water were investigated, including aldehydes, oxoacids and low molecular weight carboxylic acids. pH and ozone dosage were the parameters having the greatest effect on DBP formation. On the basis of UV absorbance measurements, the fulvic acid fractions studied taken together accurately represented the natural water and may be the primary sources of precursor material for aldehydes and oxoacid DBPs. However, as yet unidentified NOM fractions contribute significantly to carboxylic acid formation upon ozonation.     

Application of DNPH Derivatization with LC/MS to the Identification of Polar Carbonyl Disinfection Byproducts in Drinking Water

A qualitative method using 2,4-dinitrophenylhydrazine (DNPH) derivatization followed by analysis with liquid chromatography (LC)/negative ion-electrospray mass spectrometry (MS) was developed for analyzing and identifying highly polar aldehydes and ketones in ozonated drinking water. Using this method, aldehydes could be easily distinguished from ketones by differences in their mass spectra and chromatographic behavior. Results for many polar-substituted aldehyde and ketone standards are presented, as well as the identification of polar disinfection by-products (DBPs) in ozonated drinking water from full-scale plants and laboratory-scale ozonation of humic acid. One polar DBP identified has not been previously reported. This method could also potentially be used as a tool to identify carbonyl-containing DBPs from disinfectants other than ozone. However, the detection limits for the DNPH-LC/MS method are not as low as for the pentafluorobenzylhydroxylamine (PFBHA)-gas chromatography (GC)/MS method (LC/MS is typically not as sensitive as GC/MS). Therefore, it is not recommended that this method replace the PFBHA-GC/MS method, but be used as a supplement to enable the identification of highly polar carbonyl-containing DBPs that would not be possible by GC/MS.     

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.     

Formation and Removal of Biodegradable Ozonation By-Products during Ozonation-Biofiltration Treatment: Pilot-Scale Evaluation

An ozonation-biological filtration pilot-scale study was performed to evaluate the formation and removal of biodegradable ozonation by-products. The formation of aldehydes and ketoacids was found to be proportional to the DOC concentration and ozone dosage, and a strong relationship between the formation of aldehydes, ketoacids, and biodegradable dissolved organic carbon (BDOC) was observed. Four types of granular activated carbon (GAC) and one nonadsorbing medium, biolite, were employed to evaluate the performance of biofiltration for removing ozonation by-products. It was observed that GAC filters developed biological activity sooner than the biolite filter. Once developed, biofilters, either GACs or biolite, were particularly effective in the removal of aldehydes, ketoacids and BDOC.     

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.     

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.     

Effects of Different Catalysts on the Ozonation of Pyruvic Acid in Water

Removal of pyruvic acid from water has been studied through catalytic ozonation. Copper or cobalt impregnated MCM-41, Ru-Al₂O₃, Ru-CeO₂, FeO(OH) and LaTi_1-xCu_xO₃ and LaTi_1-xCo_xO₃ Perovskites have been used as catalysts. Only perovskites and Ru-CeO₂ catalysts did show significant catalytic activity to increase the ozonation of pyruvic acid.     

Ozone: A Means of Stimulating Biological Activated Carbon Reactors

To reduce the formation of chlorination byproducts in drinking water, the European strategy consists in developing techniques for the removal of organic matter. No chlorine is added to the water until the end of the treatment line, allowing a great reduction of the chlorine dose applied. Delaying the chlorination also improves the biological assimilation of organics within the filters. Identification of the basic properties (i.e., molecular weight, biodegradability) of the molecules which react with chlorine shows that the combination of ozone and biological activated carbon (BAC) filtration is an efficient and economical technique for the removal of these undesirable byproducts. More and more, drinking water suppliers are faced with the worrisome problem of chlorinated byproducts. This concern was prompted largely by the degradation of raw waters. Chlorinated byproducts are caused by the effect of chlorine on organic matter dissolved in water.     

Empirically and Theoretically–Based Models for Predicting Brominated Ozonated By–Products

During water treatment, ozonation of waters containing bromide ion producesboth organic and inorganic disinfection byproducts. Bromide ion concentrations in U.S. waters range from 0.01 to 2 mg/L (Krasner, 1989). Bromoformand dibromoacetic acid (DBAA) are the major organic byproducts and bromateion is the major inorganic byproduct derived from ozonation. Bromoform is a known carcinogen and the existence of bromate ion in water supplies also is of public health concern (Lykins, 1986). Bromate ion causes renal failure and hearing loss in laboratory animals and in human beings (Kruithof, 1992). The provisional guideline for bromate ion as proposed by the World Health Organization is 25 pg/L and may be exceeded in water treatment processesusing ozone. Also draft drinking water regulations in the U.S. will specify a maximum contaminant level (MCL) of 10 µg/L for bromate ion and a bestavailable treatment (BAT) of pH adjustment.     

Impact of Support Media on the Biological Treatment of Ozonated Drinking Water

An extensive review of the technical literature was conducted in order to determine the advantages and disadvantages of the various media used for biological filtration of ozonated drinking water. Granular activated carbon (GAC) filters were found to be significantly more efficient than conventional filters such as sand and anthracite coal. The type of activated carbon also impacted the performance of biofilters; due to their greater adsorption capacity, microporous GACs were found to be better suited than macroporus GACs.     

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.     

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.     

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.     

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.     

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.     

Influence of Ozonation of Humic and Fulvic Acids on Diuron Adsorption on Activated Carbon

The effect of ozonation on the competitor effect of humic and fulvic acids against diuron in adsorption on activated carbon in drinking water process has been studied. Ozonation treatment allows the removal of herbicides from drinking waters by modification of humic and fulvic acids structures. These latest are responsible for their adsorption variation on activated carbon. An ozone dose similar to that used in industrial pre-ozonation (1.3?mg ozone/l) does not cause significant transformations of humic and fulvic acids which could decrease their competitor effect and increase significantly the adsorption capacity of the activated carbon for a well-adsorbed pesticide like diuron.     

The Ozonation of Natural Waters: Product Identification

Aqueous solutions of fulvic acid have been ozonated under simulated water treatment plant conditions and the oxidation products identified by gas chromatography–mass spectrometry. The predominant oxidation products include numerous alkyl phthalates, mono– and di–carboxylic aliphatic acids and a few cyclic keto–compounds. Ozonation of high–fuivic creek water gave many similar products. The significance of these compounds in finished drinking water is briefly discussed.