Sources et risques de contamination dans une source d'eau potable.

摘要

The protection of drinking water sources is a new regulatory issue. Future regulations, established by the Ministry of Sustainable Development, Environment, Fauna and Parks (MDDEFP), require operators to identify catchment hazards in drinking water sources. Some risks are specific to drinking water sources in urban areas (leaky sewers, runoff on urban or industrial areas, resuspension of contaminated sediment spill of toxic products, etc.). The main objective of this project is to identify the potential contaminants that can affect a source of drinking water in urban areas, based on the case study of an urban channel whose role is to supply a drinking water treatment plant.;Several preliminary studies have identified increasing concentrations of fecal indicators in the studied urban canal during summer, and a slight contamination of the sediments by metals. In addition to identifying areas of contamination and the likely sources of these contaminants along the canal this thesis aims to assess the potential risks to a drinking water plant's intake to provide preventive and corrective measures.;Firstly, sampling campaigns identified a microbiological risk from leaking sewers affecting the quality of water and sediments from a drinking water by combining the analysis of pharmaceuticals and Escherichia coli bacteria (E. coli, fecal indicators commonly used for the detection and identification of leaky sewers) in water and sediment samples in different weather conditions. The results identify the location of a contaminated area, by leaky sewers nearby, with E. coli gradients in water and of acetaminophen and caffeine gradients in sediments. E. coli remains the best indicator of exfiltrating wastewater for a large volume of dilution and a high abundance of E. coli in the wastewater source. In addition to E. coli, pharmaceuticals, while not detected in water due to high dilution, are a good indicator of accumulated contamination from humans in sediment. This analysis has been the subject of an article submitted for publication.;Secondly, the risks to the drinking water treatment plant processes following contaminated sediment resuspension upstream from the water intake were evaluated. Thus, treatability tests at a laboratory scale were conducted to evaluate the solubility of the metals contained in the sediment and the settling velocity of the particles. The lead is by far the metal of greatest concern, being detected in sediments and water, after resuspension and at concentrations exceeding the standards. Iron and aluminium, are frequently detected in water, after resuspension, at concentrations that may affect the organoleptic quality of the treated water. Coagulation followed by filtration can remove metals in water resulting from resuspension of sediments contaminated with heavy metals. Establishing a relationship between suspended solids and turbidity will set thresholds corresponding to the turbidity concentrations of metals. An exceedance of turbidity thresholds would trigger the initiation of coagulation at the drinking water treatment plant in question.;Each part of this thesis contributes to the development of recommendations for the concerned water treatment plant. This thesis proposes an approach that can be integrated into the guide accompanying the new regulations for source water protection which will to come into force in 2013.