Microbial Responses after Disinfectant Change to Ozone in a Full-Scale Distribution System

Ozone is a promising alternative disinfectant when the concentration of organic carbon is high in the source water. The microbial responses to primary disinfectant change from monochloramine to ozone in a full-scale distribution system were investigated. Several water quality parameters including heterotrophic bacteria and a new parameter, growth potential (GP), were determined from the finished water and at three different distribution system locations before and after switching to ozone for a period of 12 months. The GP assesses the potential of the water to sustain growth of bacteria. The literature suggests that ozonation will result in a higher biodegradable organic carbon concentration and will therefore stimulate bacterial growth. Biodegradable organic carbon concentration (BDOC) and HPC increased but GP decreased after ozonation during the study period. In order to exclude seasonal effects, the data from the same seasons of the previous year were compared in the statistical analyses. Our findings showed that among the water quality parameters, HPC, disinfectant dose and total organic carbon (TOC) concentration showed statistically significant differences between the two years (paired t-test, p<0.05). When ozone was used as primary disinfectant the TOC was 1.5 times higher than when chloarmine was used, but the HPC and disinfectant dose were lower. Thus the switch of the primary disinfectant to ozone did not increase bacterial growth. At the lower dose, the disinfectant dose was effective enough to control bacterial regrowth in the distribution system during the study period.     

Ozonation of Trace Organic Compounds: Model Predictions versus Experimental Data

This paper is focused on the use of ozone for the elimination of manmade organic micropollutants from drinking waters and waste effluents requiring advanced treatment. A mathematical model was developed to simulate the physical transport and chemical oxidation phenomena prevailing during the process of ozonation. A packed column reactor was constructed in order to test the aptness of the process model. After determining the fluid-dynamic and mass transfer properties of the reactor, stock water solutions spiked with toluene were brought into contact with gaseous O₂-O₃ mixtures. Toluene removal efficiencies observed under different experimental conditions then were compared with the model predictions.     

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 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.     

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.     

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.     

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.     

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.     

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.     

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.     

Kinetic Study of the Ozonation of Some Industrial Wastewaters

Kinetic studies of the ozonation of two wastewaters released by distillery and tomato processing plants have been carried out. Once it has been assumed that an irreversible gas-liquid reaction is developed between ozone and the matter present in the water, the film theory concept was applied to this system for kinetic determinations. The evolution of the organic and inorganic matter with ozonation time has been followed by the chemical oxygen demand. The procedure allows the determination of the rate coefficients of ozone with the wastewaters treated. According to the results obtained, ozone is consumed through fast reactions which take place near the water-gas interface during an initial period. This period is used to determine the rate coefficients. Then, at more advanced ozonation times, the reactions become slower and hence they take place in the bulk of the water, articularly for the case of tomato wastewaters. Values of the rate coefficient allow us to establish both the kinetic regime of absorption and to compare the reactivity of ozone with the wastewaters and single compounds.     

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.     

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.     

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.     

The Feasibility of Using a Perfluorinated Bonded Alumina Phase in the Ozonation Process

The comparison of the efficiency of three ozonation systems (ozonation alone and ozonation in the presence of alumina or PFOA) in attempting the removal of aromatic hydrocarbons from water was made. The results obtained indicate that PFOA shows a great catalytic activity, as opposed to alumina. Moreover, ozonation in the presence of PFOA results in a much higher level of ozonation efficiency in comparison to ozonation alone. The effect of ozone dosage, catalyst dosage and pH value was investigated and was found to have a great influence on hydrocarbons removal efficiency. The degradation rate was shown to decrease with increasing ozone and catalyst dosage. The efficiency of the PFOA/O₃ system was observed to be at its greatest at the lowest pH examined.     

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.     

Tube Diameter and Height Influence on the Ozonation Operating Conditions with a U-Tube

Ozone has been used for a number of years in water treatment for viricidal and bactericidal action, as well as for its oxidizing properties. Energy consumption during its use depends on the performance of the ozone generators, but also on the ozone transfer efficiency from the gas phase to the liquid phase. Therefore, it is important to use a contactor with a high transfer efficiency.A new ozonation reactor has been developed: the Deep U-Tube (DUT). This reactor works under pressure, which increases the saturation concentration of ozone at equilibrium (C ). and creates a great turbulence, which breaks the gas bubbles and increases the interfacial area of exchange. Further, this new contactor has a piston hydraulic behavior in the liquid phase, which leads to a very great efficiency and to a better reduction for all reaction kinetics.     

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.