Antoine Montiel

Variations in trihalomethane levels in three French water distribution systems and the development of a predictive model.

Epidemiological studies have demonstrated that chlorination by-products in drinking water may cause some types of cancer in humans. However, due to differences in methodology between the various studies, it is not possible to establish a dose-response relationship. This shortcoming is due primarily to uncertainties about how exposure is measured-made difficult by the great number of compounds present-the exposure routes involved and the variation in concentrations in water distribution systems. This is especially true for trihalomethanes for which concentrations can double between the water treatment plant and the consumer tap. The aim of this study is to describe the behaviour of trihalomethanes in three French water distribution systems and develop a mathematical model to predict concentrations in the water distribution system using data collected from treated water at the plant (i.e. the entrance of the distribution system). In 2006 and 2007, samples were taken successively from treated water at the plant and at several points in the water distribution system in three French cities. In addition to the concentrations of the four trihalomethanes (chloroform, dichlorobromomethane, chlorodibromomethane, bromoform), many other parameters involved in their formation that affect their concentration were also measured. The average trihalomethane concentration in the three water distribution systems ranged from 21.6 μg/L to 59.9 μg/L. The increase in trihalomethanes between the treated water at the plant and a given point in the water distribution system varied by a factor of 1.1-5.7 over all of the samples. A log-log linear regression model was constructed to predict THM concentrations in the water distribution system. The five variables used were trihalomethane concentration and free residual chlorine for treated water at the plant, two variables that characterize the reactivity of organic matter (specific UV absorbance (SUVA), an indicator developed for the free chlorine consumption in the treatment plant before distribution δ) and water residence time in the distribution system. French regulations impose a minimum trihalomethane level for drinking water and most tests are performed on treated water at the plant. Applied in this context, the model developed here helps better to understand trihalomethane exposure in the French population, particularly useful for epidemiological studies.

Minimizing Bromate Concentration by Controlling the Ozone Reaction Time in a Full-Scale Plant

ABSTRACT The latest European Directive 98/83/CE (5 December 1998), concerning the quality of water intended for human consumption, has set a two-stage parametric value for bromate. Bromate concentration will comply with 25 μg/L after December 25, 2003, and with 10 μg/L after December 25, 2008. Bromate formation in water is generally due to bromide oxidation during the ozonation stage. Due to higher temperatures, this latter parametric value is often exceeded in summer. Minimizing bromate levels is thus a crucial problem for drinking water producers. A bromate-minimizing strategy consists of shortening the reaction time between ozone and water. This can be done by neutralizing dissolved ozone residual with bisulfite at the exit of the ozone reactor chamber and/or by managing the introduction of ozone in different chambers depending on the water flow rate. This is only possible if, in our case, the disinfection goal for ozone is respected toward bacteria and viruses. The CT value must comply with 1.6 mg/min/L. In our plants, this value could be very large due to high contact time in and after leaving the ozone reactors.

Evaluation of Bromate Ions Level Introduced by Sodium Hypochlorite During Post-disinfection of Drinking Water

During the last ten years, interest concerning the occurrence of bromate in drinking water has grown due to its potential carcinogenicity and the new regulations. One source of bromate in finished water is due to its presence in the sodium hypochlorite solutions used for the disinfection of water. In fact, the brine solutions used for the production of sodium hypochlorite contain bromide ions in varying degrees that subsequently generate a certain quantity of bromate ions. Bromate concentrations ranging from 82 to 857 mg l−1 (0.5-7.4 mg BrO3 −/g Cl2) have been found in commercial solutions of sodium hypochlorite used by Société Anonyme Gestion des Eaux de Paris (SAGEP), a company that produces drinking water for Paris, France. In addition, the chlorine concentration of the hypochlorite solution can decrease during storage, consequently the added amount of bromate increases for a given applied dose of chlorine.

Evolution of Bromates and Organobrominated Compounds in Two Drinking Water Treatment Plants

Abstract A study of concentration of bromates and THM has been made during a year on two surface water treatment plants which supply drinking water to the city of Paris. The concentrations of bromates and THM are always under die E.U guidelines, but the results on the two plants whose treatments are different (one physico-chemical, the other biological), depend on different parameters. Temperature seems to have a greater influence on the formation of bromate in the physico-chemical treatment. On the biological plant, slow sand filtration removes BDOC leading to a potentially higher formation of bromates. Concentrations of different THM are not significantly influenced by Br concentrations.

Alternatives à l'utilisation de l'atrazine. La cyanazine : moyens d'élimination

Abstract Atrazine is a pesticide frequently encountered in ground and surface waters. The maximum allowable concentration of this pesticide in France is 0.1 μg I‐1 and levels of atrazine often are over this limit. Researches are being conducted actually to treat this polluant or to find new molecules in replacement. Cyanazine has been proposed and we have tested the efficiency of differents treatments on a pilot plant. Coagulation ‐ floculation is ineffective. Ozonation seems not very effective but slow sand filtration seems better to remove this herbicide. The explanation of elimination of cyanazine on slow sand filters seems to be adsorption followed by rapid biodegradation. The step of reversible adsorption may conduct to high concentration of cyanazine in water flowing out the slow sand filter in case of brutal change of concentration in raw water.