What Does "Pure Water" Mean and How Do You Evaluate Good Drinking Water?

This article marks the beginning of a series of informative materials about drinking water. Water, the most important catalyst for life, often seems simple and ordinary to most of us: "as simple as water." In today's world, with consumer-driven economies, intensive soil exploitation, and pollution, it is far from simple. To bring these insights to the public, we have drawn upon the expertise of "the water prof," biochemist Silvia Enculescu.

From a physical and chemical standpoint, "pure water" does not naturally exist. Scientifically, it is produced only at the end of specific physico-chemical processes in laboratories—and is used exclusively for preparing reagents and culture media. Legally, this type of water is prohibited for human consumption.

Equally important, what is found in drinking water is not referred to as impurities but as its "chemical composition," defined by 45 physico-chemical parameters mandated by law. For water to be drinkable, these parameters must fall within specific values established by regulations.

Water naturally contains these compounds. Depending on their levels in the water, relative to legally permitted values, it is determined whether the water is drinkable—that is, safe and suitable for human consumption—or not.

The main parameters used to determine the potability of water are:

• pH level - It must fall between 6.5 and 9.5. A pH below 6.5 indicates acidic water, while a pH above 9.5 indicates water that is too basic. Both deviations can have immediate effects on the body (an example being the impact on stomach acidity.

• Water conductivityThis parameter measures the quantity of dissolved mineral substances in the water. Mineral water is the only exception to having a maximum conductivity value. However, it is essential to note that mineral water with a mineralization level exceeding 500 mg/l should not be consumed in quantities of two liters per day—the recommended daily intake for maintaining proper hydration in an adult human.

The higher the conductivity, the more dissolved minerals the water contains. These dissolved minerals give the water measurable electrical conductivity. The legally permitted maximum limit for water conductivity is 2500 µS/cm (microSiemens per centimeter).

• Turbidity is the parameter that reflects the quantities of mechanical impurities in water (visible even to the naked eye) — for example, clay, sand, or rust that water "carries along" from wells or the pipes through which it flows. The legal limit is five turbidity units. In the context of discussing impurities, those that are visible and measurable through turbidity are the only ones that should concern the consumer.

• Determining the presence of nitrates, nitrites, and ammonia in water is among the most important analyses. Nitrates are allowed in drinking water at concentrations up to 50 mg/L, nitrites up to 0.5 mg/L, and ammonia up to 0.5 mg/L. These chemical compounds occur naturally in water, but water from agricultural areas contains higher proportions of these compounds due to the use of chemical fertilizers.