Introduction to Non-Potable Water
Understanding the distinction between potable (drinkable) and non-potable (unsafe) water is crucial for health and survival. Water that appears clear and clean can harbor invisible threats like bacteria, viruses, and parasites. The source of the water is a primary indicator of its potability, and natural sources are often compromised by animal waste, pollutants, and geological factors. Even treated tap water can become unsafe due to infrastructure failures, necessitating boil water advisories. Therefore, knowledge of non-potable water is essential for anyone, whether in an emergency situation or dealing with compromised municipal water supplies.
Types of Water Humans Cannot Drink
Numerous types of water are unsuitable for human consumption due to various contaminants and properties. These non-potable sources range from naturally occurring water bodies to man-made and polluted water systems.
Seawater and Brackish Water
- Seawater: The high salt concentration in seawater is toxic to humans. The human body requires more water to flush out the excess salt via urination than is gained from drinking the seawater itself, leading to severe dehydration. This can cause kidney failure, delirium, and eventually death.
- Brackish Water: A mixture of freshwater and seawater, found in estuaries and deltas, brackish water is too salty for consumption but not as salty as the ocean. Like seawater, it can cause dehydration, and it may also contain other contaminants from river runoff.
Stagnant and Untreated Surface Water
- Stagnant Water: Standing, still water, such as in ponds or puddles, is a breeding ground for harmful microorganisms like bacteria, viruses, and parasites. It can also harbor insects that spread diseases. Drinking stagnant water can cause gastrointestinal illnesses like giardiasis and cryptosporidiosis.
- Untreated River and Lake Water: Even fast-moving rivers and pristine-looking lakes can contain dangerous pathogens from upstream sources, including animal feces, sewage leaks, or agricultural runoff. Never assume natural water is safe without proper purification.
Chemically and Biologically Contaminated Water
- Chemically Polluted Water: Industrial waste, agricultural runoff, and natural mineral deposits can contaminate water with toxic chemicals. Examples include heavy metals like lead and arsenic, pesticides, and nitrates. Unlike biological contaminants, these chemicals are not removed by boiling.
- Microbiologically Infected Water: Pathogenic microorganisms, including E. coli, Salmonella, and the Hepatitis A virus, can enter water sources through human and animal waste. The resulting diseases often cause severe diarrhea, vomiting, and other gastrointestinal issues.
Health Risks of Drinking Unsafe Water
Consuming non-potable water can lead to a host of health problems, ranging from acute gastrointestinal distress to chronic long-term conditions.
Waterborne Pathogens
- Bacteria: E. coli, Salmonella, and cholera-causing bacteria lead to diarrhea, vomiting, and severe dehydration.
- Viruses: Hepatitis A and Norovirus can cause liver inflammation, gastrointestinal distress, and other serious illnesses.
- Parasites: Giardia and Cryptosporidium are parasites that can cause prolonged, greasy diarrhea, fever, and stomach cramps.
Chemical and Heavy Metal Poisoning
- Heavy Metals: Exposure to lead and arsenic can cause nervous system damage, kidney failure, and increased cancer risk. Lead is especially dangerous for children, impacting brain development.
- Industrial Pollutants: Chemicals like PFAS ("forever chemicals") and pesticides can disrupt hormonal functions, cause birth defects, and lead to cancer.
Comparison of Water Types and Treatment Needs
| Water Type | Primary Contaminants | Treatability | Risk Level (Untreated) |
|---|---|---|---|
| Seawater | High salt content | Requires desalination | Very High (Dehydration, Kidney Failure) |
| Brackish Water | Salt, pathogens, chemicals | Requires desalination/purification | High (Dehydration, Illness) |
| Stagnant Water | Bacteria, parasites, viruses | Requires purification (boiling, filtering) | Very High (Gastrointestinal Disease) |
| Untreated Fresh Water | Bacteria, viruses, parasites | Requires purification (boiling, filtering) | High (Gastrointestinal Disease) |
| Chemically Contaminated Water | Heavy metals, pesticides | Often Untreatable at home | Very High (Poisoning, Chronic Illness) |
| Greywater | Soap, detergents, microbes | Requires extensive treatment | High (Illness if ingested) |
How to Make Water Safe to Drink
When facing non-potable water, proper treatment is the only way to ensure safety. The method depends on the contaminants present. For biological threats, boiling is the most effective method.
Purification Steps
- Collect Clean Water: Always collect from the clearest, most free-flowing source available, avoiding stagnant water and areas near human or animal waste.
- Filter: If the water is cloudy, use a filter (e.g., cloth, coffee filter) to remove large particles before disinfection.
- Boil: Bring the water to a rolling boil for at least one minute (three minutes at higher altitudes).
- Disinfect: In lieu of boiling, chemical tablets (like chlorine dioxide) or household bleach can be used, following specific instructions. UV light purifiers are also an option for clear water.
Warning: Never attempt to treat water contaminated with chemicals or heavy metals using these methods. The only safe option is to find an alternative water source. The U.S. Environmental Protection Agency provides comprehensive guidance on water safety during emergencies and proper disinfection methods.
Conclusion
Knowing what water can humans not drink is not merely an academic exercise—it is a matter of life and death, particularly in emergency scenarios. Seawater, brackish water, and water contaminated with human waste, agricultural runoff, or industrial chemicals are all extremely dangerous. By understanding the different types of non-potable water and the appropriate purification methods, you can make informed decisions to protect your health and the health of those around you. Always treat suspect water before consumption, and if chemical contamination is suspected, seek a safe alternative source immediately.
