Perception of drinking water in the Quebec City region (Canada): the influence of water quality and consumer location in the distribution system

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Abstract

The purpose of every water utility is to provide consumers with drinking water that is aesthetically acceptable and presents no risk to public health. Several studies have been carried out to analyze people's perception and attitude about the drinking water coming from their water distribution systems. The goal of the present study is to investigate the influence of water quality and the geographic location of consumers within a distribution system on consumer perception of tap water. The study is based on the data obtained from two surveys carried out in municipalities of the Quebec City area (Canada). Three perception variables were used to study consumer perception: general satisfaction, taste satisfaction and risk perception. Data analysis based on logistic regression indicates that water quality variations and geographic location in the distribution system have a significant impact on the consumer perception. This impact appears to be strongly associated with residual chlorine levels. The study also confirms the importance of socio-economic characteristics of consumers on their perception of drinking water quality.

Introduction

In the past few decades, public concern over the quality of drinking water has grown considerably. These concerns have arisen as a result of increased awareness about environmental pollution and episodes of waterborne disease outbreaks (Anadu and Harding, 2000). The tragedy that struck Walkerton (Canada), where seven people died of Escherichia coli contamination in the city's water distribution system in May 2000, is a sad but revealing example of the current situation. This new context is reflected in reports that an increasing proportion of residents are choosing some sort of alternative to tap water (Hudon et al., 1991, Auslander and Langlois, 1993, Therrien and Marceau, 1998, Larson and Gnedenko, 1999, Levallois et al., 1999, Anadu and Harding, 2000). In the Quebec City region, for example, Levallois et al. (1999) reported that the rejection of tap water is increasing and bottled water is being used frequently, often in alternation with tap water (43% of respondents to a survey in the region). Past studies have shown that people reject tap water mainly because of concerns about health risks (Auslander and Langlois, 1993, Anadu and Harding, 2000) or for organoleptic reasons (i.e. color, odor and taste) (Hudon et al., 1991, Levallois et al., 1999).

The goal of this study is to examine the influence of water quality variations and the geographical location of customers throughout the urban distribution system on their perceptions of tap water quality. The study revolves around a spatially based analysis of customer perceptions of the quality of tap water delivered by two water distribution systems in the Quebec City area (Canada). Several sources of information are used for the purpose of the research, including two questionnaire-based surveys on customer perceptions, data for water quality measured in the field and characteristics of the infrastructure of the distribution systems.

Every water utility aims to provide drinking water that presents no risks to public health and is, at the same time, aesthetically acceptable. Safe drinking water is generally obtained by complying with specific water quality standards established by governments. In the province of Quebec (Canada), the Ministry of the Environment recently updated the water quality standards through the promulgation of the regulation respecting the quality of drinking water (RRQDW) (Government of Quebec, 2001). The RRQDW seeks to provide added protection for public health by requiring more frequent monitoring and by updating several quality criteria which include stringent micro-organisms inactivation levels, maximum levels for treated water turbidity and for total trihalomethanes (THMs), minimum levels for free residual chlorine and control of bacteriological contamination in the distribution system such as coliform bacteria, heterotrophic bacteria (HPC) and E. coli.

While safe drinking water is assured through intensive monitoring of many organic and inorganic parameters, the protection of the aesthetic quality of drinking water—as represented by organoleptic parameters such as color, odor and taste—is much more difficult to establish. Health Canada (1996) acknowledges that some substances can represent both health risks and aesthetic problems so that both maximum acceptable concentrations (MAC) and aesthetic objectives (AO) are included in its drinking water regulations. Moreover, Health Canada recognizes that “(…) if a concentration in drinking water is well above an AO, there is a possibility of health hazards” (Health Canada, 1996).

Risk perception and drinking water quality satisfaction are closely related. Anadu and Harding (2000) define risk perception as “an individual's subjective judgment (based on aesthetic and non-aesthetic qualities) about drinking water drawn from their city water system.” This definition suggests that a consumer's perception of the risk associated with drinking water results from complicated social, cultural and psychological factors as well as an objective information. Few studies have tried to identify the driving factors behind drinking water consumption. Levallois et al. (1999) established that consumer dissatisfaction with the taste of water and knowing the source of one's drinking water are both determining factors in consumer behavior. In addition, Hudon et al. (1991) emphasized that age, income and schooling influence risk perception. Moreover, Larson and Gnedenko (1999) demonstrated how decisions made in households about drinking water consumption are related to income, consumer opinion of water quality and location in the city. Because the aesthetic quality of drinking water is usually the only basis the average consumer has in judging water quality, it seems reasonable to expect that many of those consumers will link an aesthetic problem (an unpleasant odor or taste, for example) to a potential health risk (Jardine et al., 1999). By the same token, drinking water that does not have a noticeable taste, odor or visible color may be considered by the consumer to be safe, when it actually contains contaminants with potentially adverse health effects (for example, pathogenic micro-organisms or trace organic compounds such as THMs and pesticides). In addition, microbiological contamination and high concentrations of trace organic compounds are not necessarily associated with degradation in the aesthetics of drinking water (Jardine et al., 1999).

Chlorine constitutes the most common disinfectant used in the drinking water industry throughout the world. It is used as a disinfectant agent during treatment in order to deactivate various types of micro-organisms (Connell, 1996). In addition, when it is leaves the treatment plant, water requires a residual amount of chlorine, which acts as a protection against microbiological re-growth during its journey through the distribution system (Hass, 1999). However, in some cases, bacterial re-growth can occur even if residual chlorine is present (Geldreich, 1996). Concentrations of the residual chlorine decrease as the water moves through the system and, particularly in large utilities, may become very low and even undetectable at the extremities (Powell et al., 2000, Rodriguez and Sérodes, 2001). These extremities are characterized by a high residence time of water and by an important degree of ‘intimacy’ between the bulk water and the pipe, especially when pipe diameters are small. This encourages reactions between water constituents and pipe material, which can result in deposits of organic and inorganic material, the corrosion of iron-based pipes and the development of an undesirable biofilm on the inner walls of pipes, particularly during summer months. These phenomena, combined with low residual chlorine levels, favor the decay of the microbiological water quality, in particular when water temperatures are high. Other phenomena, which occur mostly at system extremities, include the precipitation of inorganic material, causing an increase in turbidity levels, and the occurrence of diverse off-flavor problems originating from micro-organism metabolism and pipe deterioration (Goodrich, 1989).

Maintaining sufficient levels of residual chlorine throughout the distribution system is the best bet for reducing the risks of microbiological contamination. Increasing the chlorine doses applied in the treatment plant or in booster stations throughout the system may keep residual chlorine levels up, and thus provide better protection against microbial contamination. However, this approach has some important drawbacks. Chlorine reacts with natural organic matter dissolved in drinking water, generating potentially carcinogenic chlorination by-products (CBPs) such as THMs. Generally, CBP levels increase when the reaction time of chlorine water compounds increase, thus they are highest in the distribution system's extremities (Rodriguez and Sérodes, 2001). In addition, several odor and taste problems appear to be linked to high levels of residual chlorine, prompting frequent customer complaints (Yohe et al., 1986). Krasner and Barrett (1984) established the taste-threshold of free residual chlorine to be 0.24 mg/l.

After being treated in the plant, the quality of drinking water varies along its path through the distribution system. Even if it complies with regulation standards as it leaves the plant, several investigations have demonstrated that water quality (both physicochemical and microbiological) deteriorates as it moves from the treatment plant to the system extremities (American Water Works Association, 1985, Rodriguez et al., 1994, Powell et al., 2000, Rodriguez and Sérodes, 2001). It has been clearly established that these variations are closely associated with the variations of water residence time throughout the distribution system (Ozdemir, 1999). It is reasonable, then, to hypothesize that customer perception of water quality will vary spatially within a distribution system as well. There are, however, no reported investigations in the existing literature about the impact of geographical location and water quality in the distribution system on people's perception of tap water.

Section snippets

Cases under study

The case study areas selected are two adjoining municipalities in the greater Quebec City area of Canada: Sainte-Foy and Quebec City (Table 1). Each is served by its own treatment plant and distribution system. These utilities represent interesting profiles for research purposes because the quality of their raw water is quite different. Quebec City's water source is only slightly affected by anthropogenic pollution, but has very high color originating mainly from vegetation decay. The

Socio-economical characteristics of sectors

Table 3 presents the main socio-economic variables of the respondents for the 2001 survey, according to the established locations throughout the distribution systems. Respondents to the 2001 survey were older, had more income and a higher level of education in comparison to respondents of the 1994 survey (not shown in Table 3). This result is normal, given that in 2001, the survey was directed only to single family dwellings probably occupied by owners with higher income, whereas in 1994, the

Conclusions

Based on two surveys and on complementary information, this study has shown that variations in water quality and geographic location of consumers within the distribution system have a considerable impact on perception of tap water quality. However, this impact seems closely related to residual chlorine levels, which explains why consumers living near the water treatment plant are generally less satisfied with the quality of tap water, and perceive more risk associated with it than people living

Acknowledgements

Authors thank Quebec City's water utility and its Environmental Service. Special thanks are due to François Proulx, Jean-René Houle and Damien Roy for their generous collaboration. We are also grateful to Mr Jacques Grondin and Mrs Suzanne Gingras from the Public Health Centre of the Quebec City region for permission to use the 1994 survey database. This project has been funded by the Centre for Research in Regional Planning and Development (CRAD of Laral University).

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