Water is essential for life, but not all water sources are safe for drinking. Potable water, or drinking water, refers to water that is free from contaminants and safe for human consumption. Understanding what makes water potable and how to make non-potable water safe to drink is key for individual and public health.
What Is Potable Water?
Potable water, also known as drinking water or potable drinking water, is water that is safe to drink or use for food preparation without risk of health issues. For water to be considered potable, it must meet certain water quality standards for human consumption.
Specifically, potable water must:
- Be free from infectious agents like bacteria, viruses, and parasites. Common disease-causing microbes found in contaminated water include E. coli, Giardia, Cryptosporidium, and Salmonella.
- Contain minimal levels of harmful chemicals such as arsenic, lead, nitrates, and pesticides. These can have toxic effects on the body.
- Have acceptable levels for aesthetic qualities like appearance, taste and odor. Discoloration, unpleasant smell or taste can make water unpalatable to drink.
Water Quality Guidelines
There are guidelines and regulations in place to ensure drinking water safety. In the United States, the Environmental Protection Agency (EPA) sets legal standards for drinking water quality under the Safe Drinking Water Act.
The EPA’s National Primary Drinking Water Regulations cover over 90 contaminants. Maximum allowable levels are set for each as well as water testing schedules. Public water systems must meet these standards. Private wells are recommended to follow them too but it is not required by federal law.
Some drinking water standards include:
- Microbes: zero total coliforms and E. coli per 100 mL sample
- Nitrates: 10 mg/L or 10 ppm maximum
- Arsenic: 0.01 mg/L or 10 ppb maximum
- Lead: 0.015 mg/L or 15 ppb maximum
The World Health Organization (WHO) also publishes Guidelines for Drinking-Water Quality as a reference for setting national standards worldwide. Many countries model their potable water regulations after the WHO standards.
How to Know if Water is Potable
Determining if water is potable requires testing and analysis. Some signs that water may not be suitable for drinking include:
Appearance and Odor
- Cloudiness or murkiness
- Discoloration – brown, red, green, black
- Strong odor – sulfurous, sewage-like
These suggest contamination by particles, organic matter, chemicals, or gases.
Taste
- Salty or brackish taste indicates high mineral content
- Metallic taste may mean presence of iron, copper, or manganese
Gastrointestinal Distress
- Nausea, vomiting, diarrhea after drinking point to waterborne pathogens or toxins.
However, the only way to confirm water potability is through laboratory testing. Key water quality parameters experts test for include:
- Microbiological – test for bacteria like E. coli, viruses, protozoan parasites.
- Chemical – check levels of inorganic chemicals like heavy metals, pesticides, fertilizers.
- Physical – turbidity, temperature, pH and dissolved solids.
- Radiological – measure radiation from decay of natural elements like uranium.
Municipal water systems perform required testing to verify safety. Private well owners need to arrange for water testing, at least annually.
How is Water Made Potable?
Water treatment processes remove contaminants to make non-potable water safe to drink. Treatment steps depend on the water source – surface water or groundwater.
Treating Surface Water
Surface water from lakes, rivers, reservoirs require extensive treatment due to higher levels of contamination. Here are typical steps:
1. Screening
Screens out large debris like sticks, leaves, trash that could damage equipment.
2. Coagulation and Flocculation
Destabilizes suspended particles by adding coagulant chemicals like aluminum sulfate. Slow mixing causes particles to stick together into larger clumps that settle out.
3. Sedimentation
Allows floc to settle out by gravity, removing most suspended solids.
4. Filtration
Filters out smaller particles like silt, clay and microbes suspended in water. Common filters used – sand, activated carbon, membrane filters.
5. Disinfection
Kills bacteria, viruses, parasites. Chlorine is the main disinfectant used. Ozone, UV light also help deactivate pathogens.
6. Storage and Distribution
Treated water is stored in tanks before distribution. Disinfectant residual is maintained to prevent microbial regrowth in pipes.
Treating Groundwater
Groundwater from wells and boreholes generally require less treatment than surface sources. The earth acts as a natural filter. Main steps include:
- Oxidation – Removes iron, manganese by converting to solid form for filtering
- Disinfection – Chlorination to kill microbes
- Fluoride addition – Adjusts natural fluoride levels which prevent tooth decay
Some other treatment processes used for specific contaminants in groundwater:
- Water softening – Removes minerals like calcium and magnesium
- Activated alumina – Removes arsenic
- Reverse osmosis – Desalinates brackish water high in dissolved salts
How to Make Non-Potable Water Safe to Drink
In emergency situations or remote locations, it may be necessary to treat water yourself to make it potable. Here are some options:
Boiling
Boiling water vigorously for 1 minute kills most viruses, bacteria, and parasites. Cool before drinking. Boiling prolongs water shelf life but does not remove heavy metals, salts, or chemicals.
Chemical Disinfection
Adding chlorine bleach or iodine tablets inactivates microorganisms. 1/8 teaspoon bleach treats 1 gallon of clear water. Double for cloudy. 30 mins contact time. Use bleach meant for disinfection.
Solar Disinfection (SODIS)
Exposing water in clear bottles to sun for 6 hours treats microbiological contaminants. Sunlight and heat damage pathogens. Turbid water should be filtered first.
Ceramic Filtration
Porous ceramic filters mechanically trap bacteria and protozoa. Must be used with disinfectant to also remove viruses.
Survival Straws
Portable drinking straws with built-in carbon and/or ultrafiltration membranes filter out bacteria, protozoa as you sip. Does not fully treat viruses.
Distillation
Heating water to collect pure vapor is effective for any type of contaminated water. Requires significant energy input.
When possible, start with the cleanest water source available and use a combination of methods for full potability. Various commercial portable water treatment systems are also available.
Testing Treated Water
Check treated water using field test kits which detect fecal bacteria like E. coli. Absence confirms microbial removal. Check for residual disinfectant if used. If no field kits, use other senses or wait 48 hours before drinking if water seemed risky.
Frequently Asked Questions About Potable Water
How much water should you drink daily?
The recommended daily intake of water from fluids and food is about 15.5 cups (3.7 liters) for men and 11.5 cups (2.7 liters) for women. Actual needs vary based on climate, activity level and health status. Drink more in hot weather or when ill or exercising. Thirst is an indicator to drink more.
Is tap water potable?
Tap water from public water systems in developed countries is tightly regulated to ensure it is potable for human consumption. In the U.S., EPA enforces drinking water standards requiring disinfection and frequent testing for hundreds of potential contaminants.
Can you drink rain water?
Rainwater is generally safe from viruses and bacteria which cannot survive long in the atmosphere. However, rain can collect air pollutants, bird droppings and contaminants from roofing and storage containers. Boiling or disinfection is recommended. Proper collection and storage is key.
Is bottled water safer than tap water?
The EPA sets higher safety standards for tap water than the FDA’s bottled water rules. Both undergo similar disinfection and filtration processes. Bottled water offers portability but is not necessarily purer or safer than properly treated municipal tap water.
What water should you avoid drinking?
Avoid drinking untreated surface water which can harbor dangerous pathogens like Giardia, Cryptosporidium or harmful algae blooms. Water directly from a lake, river or stream should always be treated. Also avoid well water testing positive for chemicals like arsenic or microbes like E. coli.
Can old pipes contaminate water?
galvanized steel or lead service lines and household plumbing can leach toxic metals over time. Let tap water run a few minutes before using for drinking or cooking if plumbing contains lead. Water systems treat to prevent lead corrosion. Consider testing home plumbing.
How to clean a water storage container?
Disinfect drinking water containers regularly. Wash with soap first, then rinse. Sanitize using a bleach solution (1 tsp per gallon of water). Let stand 5 min, rinse out bleach taste. Air dry upside down.
What are the health risks of drinking unsafe water?
Drinking contaminated water can cause infectious diseases like typhoid, cholera, dysentery, hepatitis A, giardiasis. Toxic chemicals, metals or radiation create risk for cancer, organ damage, birth defects. Unsafe water kills over 800,000 people each year.
Can water be too clean to drink?
Highly purified water may lack adequate minerals for human health. Distillation and deionization remove almost all dissolved solids including beneficial calcium, magnesium, and fluoride. Low mineral water has flat, insipid taste. Moderate mineralization is ideal.
Conclusion
Having access to clean and safe drinking water is vital for public health. While regulations mandate treatment for public supplies, individual water sources should also be tested and made potable if necessary. Treating water by filtration, disinfection, boiling, or other methods can remove disease-causing contaminants and prevent waterborne illnesses. With some knowledge and care, non-potable water can be made fit for human consumption.
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