Les goûts et les odeurs dans l’eau potable : revue des composés responsables et des techniques de mesure

L’évaluation de la qualité de l’eau potable d’un réseau de distribution est souvent faite en tenant compte des normes physico-chimiques et microbiologiques édictées par les réglementations nationales. L’approche par barrières multiples permet aussi d’assurer aux consommateurs une eau avec une sécurité sanitaire optimale. Cependant, malgré les sommes investies par les municipalités pour se conformer à ces normes, les consommateurs renoncent fréquemment à consommer l’eau du robinet.Ce refus peut être attribué, entre autres, à la qualité organoleptique (goût, odeur) de l’eau distribuée par les réseaux d’aqueduc. Toutefois, cet aspect est peu pris en compte par les législations actuelles et, conséquemment, est peu considéré par les gestionnaires des réseaux d’eau potable. De plus, les méthodes utilisées pour évaluer les molécules responsables des goûts et des odeurs de l’eau distribuée exigent de l’équipement spécialisé et coûteux. Cet article présente une revue de la problématique des composés responsables des goûts et des odeurs. Les aspects concernant les origines de ces composés, les méthodes quantitatives et qualitatives développées jusqu’à présent pour les analyser et la faisabilité d’application desdites méthodes, selon leurs avantages et leurs limites, seront abordés.The assessment of drinking water quality in a distribution system is generally based on physicochemical and microbiological standards set by government regulations. Although municipalities often invest considerable amounts to comply with regulations, an increasing proportion of citizens prefer alternatives to tap water. This situation may be in part explained by the organoleptic quality of distributed water in municipal systems and, in particular, by taste and odours. However, taste and odours are rarely considered as water quality criteria by municipal water managers. Moreover, analytical methods used to analyze molecules related to taste and odours in drinking water require specialized and costly equipment. This article presents the state of the art in terms of taste and odour issues in the drinking water area. The paper focuses on the origins of taste and odours and on the methods (qualitative and quantitative) available for the analysis of the compounds from which they originate. The feasibility of applying these methods to water quality surveillance is discussed, along with their advantages and drawbacks

Identification of dichloroacetic acid degrading Cupriavidus bacteria in a drinking water distribution network model

Aims: Bacterial community structure and composition of a drinking water network were assessed to better understand this ecosystem in relation to haloacetic acid (HAA) degradation and to identify new bacterial species having HAA degradation capacities. Methods and Results: Biofilm samples were collected from a model system, simulating the end of the drinking water distribution network and supplied with different concentrations of dichloroacetic and trichloroacetic acids at different periods over the course of a year. The samples were analysed by culturing, denaturing gradient gel electrophoresis (DGGE) and sequencing. Pipe diameter and HAA ratios did not impact the bacterial community profiles, but the season had a clear influence. Based on DGGE profiles, it appeared that a particular biomass has developed during the summer compared with the other seasons. Among the bacteria isolated in this study, those from genus Cupriavidus were able to degrade dichloroacetic acid. Moreover, these bacteria degrade dichloroacetic acid at 18°C but not at 10°C. Conclusions: The microbial diversity evolved throughout the experiment, but the bacterial community was distinct during the summer. Results obtained on the capacity of Cupriavidus to degrade DCAA only at 18°C but not at 10°C indicate that water temperature is a major element affecting DCAA degradation and confirming observations made regarding season influence on HAA degradation in the drinking water distribution network. Significance and Impact of the Study: This is the first demonstration of the HAA biodegradation capacity of the genus Cupriavidu

The assessment of population exposure to chlorination by-products: a study on the influence of the water distribution system

<p>Abstract</p> <p>Background</p> <p>The relationship between chlorination by-products (CBPs) in drinking water and human health outcomes has been investigated in many epidemiological studies. In these studies, population exposure assessment to CBPs in drinking water is generally based on available CBP data (e.g., from regulatory monitoring, sampling campaigns specific to study area). Since trihalomethanes (THMs) and haloacetic acids (HAAs) are the most documented CBP classes in drinking water, they are generally used as indicators of CBP exposure.</p> <p>Methods</p> <p>In this paper, different approaches to spatially assign available THM and HAA concentrations in drinking water for population exposure assessment purposes are investigated. Six approaches integrating different considerations for spatial variability of CBP occurrence within different distribution systems are compared. For this purpose, a robust CBP database (i.e., high number of sampling locations selected according to system characteristics) corresponding to nine distribution systems was generated.</p> <p>Results and conclusion</p> <p>The results demonstrate the high impact of the structure of the distribution system (e.g., presence of intermediary water infrastructures such as re-chlorination stations or reservoirs) and the spatial variability of CBPs in the assigned levels for exposure assessment. Recommendations for improving the exposure assessment to CBPs in epidemiological studies using available CBP data from water utilities are also presented.</p

Haloacetic acid degradation by a biofilm in a simulated drinking water distribution system

Haloacetic acids (HAAs) are disinfection by-products formed as a result of the reaction between chlorine and natural organic matter found in water. HAA concentrations have been observed to decrease at distribution system extremities. This decrease is associated with microbiological degradation by pipe wall biofilm. The objective of this study was to evaluate HAA degradation in a drinking water system in the presence of a biofilm and to identify the factors that influence this degradation. Degradation of dichloracetic acid (DCAA) and trichloroacetic acid (TCAA) was observed in a simulated distribution system. The results obtained showed that different parameters came into play simultaneously in the degradation of HAAs, including retention time, water temperature, biomass, composition of organic matter, and pipe diameter. Seasonal variations had a major effect on HAA degradation and biomass quantity was lower by 1 to 2 logs in the winter and spring compared with the fall. HAA removal decreased with increasingly large pipe diameters. The specific effects of each of these factors were difficult to isolate from each other owing to interactions