Part 1 (Parameters used in drinking water)

To maintain people’s health and well-being, tap water must meet many requirements in quality. Quality standards are therefore defined depending on the country. They are generally inspired by international directives, such as the directives on drinking water quality defined by the World Health Organization. It is essential to know the parameters present in these standards.

Drinking water is characterized by three types of parameters :

Physical parameters

Chemical parameters

Bacteriological parameters

What can we find within each of these groups of parameters?

We will discuss the different physical parameters, then the chemical parameters, and finally the bacteriological ones.

Organic compounds, such as humic substances, and inorganic compounds such as dissolved iron or manganese, are responsible for color, odor, and taste. We also call this the water’s flavor. Water can, therefore, have a more or less brown color, a taste, and an earth-like odor or one of chlorine in the case of overdosage of disinfectant.

Sensory organs quickly identify and perceive these parameters. These parameters are called organoleptic properties.

Other physical parameters are also important such as temperature, pH i.e. acidity and alkalinity, conductivity which corresponds to the level of salt in water, and turbidity which is the presence of fine particles that cloud the water.

These are the physical parameters that must be controlled in drinking water.

From a chemical point of view, a great number of compounds can be found. Some of the most important examples are cited here.

The first is Total Organic Carbon (the acronym of which is written TOC) is comprised of all the organic molecules present in water following treatment. It covers all residual humic substances, sugars, proteins and amino acids, and some micropollutants.

Organic micropollutants, often due to human activity, are pesticides, insecticides, herbicides, or solvents.

Inorganic substances due to interactions between air containing carbon dioxide and water are found, especially :

Carbon dioxide and carbonate anions;

Hydrogen carbonate.

These substances, in equilibrium in water, are essential for water intended for human consumption.

Amongst inorganic micropollutants, nitrogen-containing substances such as ammonium, nitrites, and nitrates are also found. The presence of metallic cations and anions is also observed.

The third major group of parameters is bacteriological parameters.

Bacteria are present everywhere in living beings, in the environment, in the ground, in water, and in the air.

They are found in raw water to be processed for drinking water and in treatment processes, the last stage of which is often disinfection.

For this disinfection operation, oxidants such as bleach, ozone, gaseous chlorine, hydrogen peroxide, or chlorine dioxide are used.

The microbiological analysis of water intended for human consumption is not conducted to complete an inventory and to determine the quantity of all the bacteria present, but to look for bacteria that are likely to be pathogens and determine their concentration.

The presence of bacteria is most often the cause of water not being drinkable.

Two bacterial families should be sought and quantified: Escherichia Coli and Enterococci.

Escherichia Coli are Gram-negative bacteria and are very common in humans. It is a fecal indicator. Some E. Coli strains are pathogenic causing gastroenteritis, urinary infections, meningitis, or sepsis.

Enterococci are Gram-positive bacteria that are often found in short chains. They are opportunistic pathogens causing blood poisoning, and urinary or abdominal infections of intestinal origin.

What you need to remember about the parameters of drinking water.

Three types of major parameters are differentiated in drinking water quality standards :

Physical parameters that cover organoleptic properties, pH, and temperature;

Chemical parameters including amongst others, the concentration of total organic carbon and micropollutants;

Bacteriological parameters whose main markers are the presence or absence of Escherichia Coli and Enterococci.

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