Drinking water quality has been in the news recently with concerns about pharmaceuticals being present in the water and looming shortages. A recent article in Business Week discusses Boone Pickens interest in the water business because it is going to be the next commodity in short supply. As a result, many people are concerned that in the US and around the world we are running out of good sources of drinking water. In fact, some parts of the US we are recovering water from sewage treatment plants for reuse as drinking water. At this point most of that “reclaimed water” is being used for non potable applications, but If the drinking water plant that supplies your water from is located downstream of a wastewater treatment plant, at least some of the water you are consuming is recycled.
There is nothing to worry about here. The quality of water from drinking water treatment facilities is closely monitored and regulated by both state and federal agencies. Our water is safe to drink and amazingly inexpensive. In fact, water quality is getting better all of the time due to increasingly stringent regulation from the EPA. Some of the more recent regulations have been designed to prevent dangerous micro organisms from making people ill. Other regulations have reduced the amount of chlorinated organic chemicals, potential cancer causing compounds, from entering the drinking water supply.
Improvement in water quality has been made possible by advancements in water treatment technologies including membrane filtration, UV radiation and ozone water treatment. Ozone is particularly interesting since it has the capability to solve many water treatment problems at the same time.
Ozone is a form of oxygen that has three oxygen atoms instead of two. The chemical formula for ozone is O3 whereas the chemical formula for oxygen is O2. One of the advantages of ozone in water treatment is that it is not stable and eventually reverts back to oxygen in water. Thus it leaves no harmful residuals after it has completed its work. As a result, O3 is used for many different applications in drinking water including:
- Disinfection of difficult to treat micro organisms that can make people seriously ill
- Disinfection without the formation of potentially cancer causing chemicals
- Removal of micro pollutants such as pesticides and pharmaceuticals
- Removal of unpleasant tastes, odors and colors that make water difficult to use
Ozone is produced in a machine called an ozone generator. These machines convert oxygen to ozone. The oxygen can come from air or from a purer form of oxygen. The ozone/oxygen gas mixture is then injected into water where it removes chemical compounds and kills micro organisms. Ozone has been used for this purpose in Europe for over 100 years. Over the last century, the technology for producing O3 has significantly improved making it more efficient and less expensive.
Ozone has only been in large scale use in the United States for about 30-40 years. Many major cities have decided to use ozone to treat their drinking water including Los Angeles, Boston, Orlando, Dallas, Tacoma, Detroit, San Francisco, Milwaukee, and Phoenix. In total over 300 cities in the US treat water with O3. In addition, almost all bottled water sold in the United States is ozonated.
Technologies like ozone are allowing cities and water utilities to use a wider array of water sources including wastewater to expand the supply of water while keeping costs under control. This will become important as cities in arid regions of the US continue to grow rapidly and need additional supplies of water to serve their populations.