Potable water is water safe for human consumption, used for drinking, cooking, and personal hygiene without health risks. Access to safe drinking water is essential for public health, supporting biological functions and preventing waterborne diseases.
What Makes Water Potable
Potable water must meet specific physical, chemical, and biological criteria to be considered safe. This includes the absence of harmful microorganisms like bacteria, viruses, and parasites, which can cause severe illness. Safe drinking water also contains minimal concentrations of toxic chemicals, such as heavy metals, pesticides, and industrial pollutants.
Beyond chemical and biological purity, potable water exhibits desirable physical properties. It should have low turbidity, meaning it is free from suspended solids that can make it cloudy. Potable water should also be free of unpleasant tastes or odors, which can indicate contaminants.
How Potable Water is Produced
Raw water sources for potable use often include surface waters like rivers and lakes, as well as groundwater from aquifers. These sources typically contain impurities that necessitate treatment before the water is safe to drink. The initial step in water treatment often involves screening to remove large debris, followed by aeration to improve taste and odor and remove dissolved gases.
Following initial preparation, water undergoes coagulation and flocculation, where chemicals are added to clump small particles into larger, heavier flocs. These heavier particles then settle out during sedimentation. The water then moves to filtration, passing through layers of sand, gravel, and charcoal to remove remaining suspended particles and some microorganisms. Finally, disinfection, commonly using chlorine or ultraviolet light, eliminates any lingering harmful bacteria and viruses, ensuring the water’s microbial safety before distribution.
Substances That Impair Water Safety
Various contaminants can render water non-potable, posing significant health risks to consumers. Biological contaminants, such as bacteria like E. coli, viruses like norovirus, and parasites like Giardia and Cryptosporidium, originate primarily from human and animal waste. Ingesting these can lead to acute gastrointestinal illnesses, including diarrhea, vomiting, and fever.
Chemical contaminants encompass a broad range of substances. Heavy metals like lead can leach from old plumbing, potentially causing developmental issues in children and neurological problems in adults. Arsenic, a naturally occurring element, can contribute to skin lesions and various cancers with long-term exposure. Industrial pollutants and agricultural runoff containing pesticides and nitrates also pose risks, potentially impacting neurological function or causing blood disorders. Physical contaminants, such as sediment and excessive turbidity, do not always directly cause illness but can shield microorganisms from disinfectants and indicate the presence of other harmful substances.
Maintaining Water Quality Standards
Ensuring water remains potable is an ongoing process supported by regulatory frameworks and continuous monitoring. Governmental bodies establish and enforce strict standards for drinking water quality. These standards specify maximum contaminant levels and outline required treatment techniques.
In the United States, the Environmental Protection Agency (EPA) sets national standards under the Safe Drinking Water Act (SDWA), enacted in 1974. This act mandates public water systems regularly test for contaminants and notify customers of violations. Globally, the World Health Organization (WHO) publishes guidelines for drinking water quality, providing a basis for countries to develop their own regulations.