Water Quality

When we talk about water quality, we distinguish between two main aspects:

1. Bacteriological (Microbiological) Quality

This checks whether the water has been contaminated by dangerous microorganisms (often of fecal origin). Pathogenic germs are invisible, odorless, and tasteless: clear water can be very dangerous.

2. Physicochemical Potability

This checks whether certain chemical or physical parameters exceed safe levels for health (nitrates, nitrites, pH, etc.). Here too, water may appear “good” but be unfit for consumption.

1) Bacteriological tests: the essentials

Microbiological analyses rely on “indicator organisms.” They are not always dangerous in themselves, but their presence indicates that contamination has occurred and that more serious microbes may be present.

Key parameters and standard potability criteria:

• E. coli: Primary indicator of fecal contamination. Its presence indicates a direct risk of diarrheal diseases, typhoid, cholera, etc.
• Intestinal enterococci: A robust indicator of fecal contamination, particularly useful for groundwater and springs.
• Total coliforms: Indicators of general hygiene and deficiencies in treatment or protection of the water system.
• Clostridium perfringens (spores): Indicates past contamination or poor filtration.

2) Potability tests (physicochemical): parameters to monitor

Examples of widely used guideline values (WHO / EU):

• pH: between 6.5 and 9.5 Outside this range, the water may become corrosive or irritating, and promote the leaching of metals.

• Turbidity: High turbidity can protect microbes and reduce the effectiveness of disinfection.

• Nitrates: ≤ 50 mg/L Above this level: risk of methemoglobinemia in infants (“blue baby syndrome”) and other health effects.

• Nitrites: ≤ 0.5 mg/L Often indicate recent pollution or the conversion of nitrates. Toxic at high doses.

• Conductivity: ≤ 2500 µS/cm Provides an indication of mineralization: too high = water with a high salt content, sometimes linked to pollution.