Definition of Purified Water

There are several different terms used to describe the processes and sources of bottled water, and it can all be very confusing. The Food and Drug Administration (FDA) regulates these terms and bottled water standards. According to the United States Pharmacopeia (USP), purified water is water that has been produced through the methods of either reverse osmosis, deionization, distillation or other methods that meet USP standards to remove impurities.

Purification by distillation

The distillation method is a process of purifying water in which the water is heated and converted to water vapor (steam). As the vapor cools, it condenses and the liquid is collected. Distilling water removes both organic and inorganic particles. This includes radioactive materials, bacteria and also all minerals.

Purification by reverse osmosis

In reverse osmosis, the goal is to have one solution with all of the solutes and another solution of just water, rather than both the water and the solutes on both sides of the membrane. Pressure is applied to the higher concentration solution, overcoming the osmotic pressure and forcing water across the membrane. The water is then virtually solute free.

Purification by filtration

Water obtained from a municipal source and bottled for consumption is labeled as "drinking water." Drinking water is purified using one or several methods including disinfection, sedimentation, charcoal filtration, clarification and/or deionization. These treatments remove organic and inorganic contaminants, reduce turbidity and improve taste. This water is the most similar to tap water.

Tap Water

Tap water is required to meet the same FDA purification standards as bottled water and these standards are regulated by the Environmental Protection Agency (EPA).

Speculation

Different purification methods remove different types of contaminants, and the levels of contaminants that remain after treatment vary. These levels must still be below FDA standards. There is speculation regarding the safety of tap water for drinking purposes as well as the healthiness of water from which minerals have been removed. There have been no definitive studies proving that either is unhealthy.

References

• Water Law and Standards
• FDA Drinking Water Regulations

Resources

• EPA Drinking Water Standards