Drinking water
Drinking water, also known as potable water, is water that is safe for human consumption and suitable for drinking, cooking, and personal hygiene. It is essential for human survival and plays a fundamental role in maintaining public health, supporting biological processes, and sustaining life on Earth.
On our planet, fresh water suitable for human use makes up only a tiny fraction of the total water volume — about 2.5–2.6% of all water on Earth, which totals roughly 1.386 billion cubic kilometers. That is, about 34.65 million km³ is fresh water.
However, most of this fresh water is inaccessible:
- ≈68.7% is locked in glaciers and permafrost,
- ≈30% is stored underground (often too deep to extract),
- More than 1% exists as surface water in lakes, rivers and swamps.
In fact, only about 0.007% of all Earth’s water is readily available for human use — found in rivers, lakes, and shallow aquifers.
To illustrate: if all Earth’s water were 100 liters, the amount of accessible drinking water would be just 0,007 liters — roughly half a teaspoon.
Composition and Properties
Drinking water is a liquid composed primarily of the chemical compound H₂O, but it may contain small amounts of dissolved minerals, gases, and organic matter. Natural water sources often include substances such as calcium, magnesium, sodium, potassium, bicarbonates, chlorides, and sulfates.
The physical properties of water include:
- Melting point: 0 °C (32 °F)
- Boiling point: 100 °C (212 °F) at 1 atm
- Density: approximately 1 g/cm³ at 4 °C
For water to be considered potable, its chemical and biological composition must meet established quality standards defined by international or national regulations, such as those of the World Health Organization (WHO), the U.S. Environmental Protection Agency (EPA), or the European Union Drinking Water Directive.
Drinking water sources
Drinking water originates from both surface and groundwater sources:
Surface water: includes rivers, lakes, and reservoirs; it is typically treated before consumption.
Groundwater: found in aquifers, wells, and springs; it is often naturally filtered through soil and rock layers.
Rainwater: can be collected and purified for use in regions with limited access to other sources.
Desalinated water: produced by removing salts and impurities from seawater or brackish water, commonly used in arid regions.
Treatment and Purification
Before distribution, water usually undergoes a series of treatment processes designed to remove contaminants and pathogens. Common stages include:
- Coagulation and Flocculation – chemicals are added to bind suspended particles.
- Sedimentation – heavy particles settle at the bottom.
- Filtration – water passes through layers of sand, gravel, and charcoal.
- Disinfection – microorganisms are destroyed, often using chlorine, ozone, or ultraviolet (UV) radiation.
In some cases, advanced treatment technologies such as reverse osmosis, activated carbon filtration, or membrane ultrafiltration are applied to improve water quality and taste.
Health and Nutrition
Water is essential for maintaining homeostasis in the human body. It regulates temperature, aids digestion, transports nutrients, and removes waste. On average, an adult requires approximately 2 to 3 liters of water per day, depending on factors such as climate, physical activity, and diet.
Insufficient water intake leads to dehydration, which can cause fatigue, dizziness, and impaired cognitive and physical performance. Prolonged dehydration may lead to serious health problems. Conversely, excessive water intake can result in hyponatremia, a condition characterized by dangerously low sodium levels in the blood.
Water Quality and Standards
The quality of drinking water is determined by physical, chemical, and microbiological parameters. Key indicators include:
- Turbidity (clarity)
- pH level
- Total dissolved solids (TDS)
- Presence of heavy metals (lead, mercury, arsenic)
- Microbiological safety (absence of Escherichia coli, Salmonella, and other pathogens)
Organizations such as the WHO publish guidelines that specify permissible limits for these parameters. Compliance with such standards is essential to prevent waterborne diseases, including cholera, dysentery, typhoid fever, and hepatitis A.
Distribution and Access
In most urban areas, potable water is supplied through municipal water systems consisting of treatment plants, storage facilities, and distribution networks. In rural or remote regions, access may depend on wells, boreholes, or natural springs.
According to the United Nations, as of the early 21st century, approximately 2 billion people worldwide lack access to safely managed drinking water services. This shortage poses significant challenges for global health and development.
Environmental and Economic Aspects
The management of drinking water resources is closely linked to environmental sustainability. Overextraction, pollution, and climate change threaten the availability of freshwater. Sustainable water management involves protecting watersheds, reducing pollution, recycling wastewater, and promoting efficient water use.
The bottled water industry represents a significant economic sector, but it also contributes to plastic waste and environmental degradation. In contrast, improving the quality of public tap water systems offers a more sustainable and cost-effective solution.
Future Challenges
Future challenges include ensuring equitable access to safe drinking water, developing climate-resilient infrastructure, and promoting technological innovation in water treatment and conservation. Global cooperation and responsible governance are required to protect this essential resource for future generations.
