The city of Modesto, Calif., agreed to pay a $165,000 fine...
UV-based technology combats waterborne pathogens in drinking water
Since 1993, increased and more stringent water treatment
rules by the U.S. EPA have intensified the need for a comprehensive,
cost-effective solution to treat Cryptosporidium, Giardia and other
waterborne pathogens in drinking water.
The solution was not chlorine, as it did not have an effect
on Cryptosporidium unless applied in
such toxic levels that it became dangerous to humans. Furthermore, independent
research and testing sponsored by the water treatment industry confirmed that
ultraviolet (UV) radiation was ineffective for fighting Cryptosporidium except in extremely high doses, making UV treatment
In 1996, the Calgon Carbon Corp. took a different approach
and tested a new theory that showed Cryptosporidium and other parasites, including Giardia, could be
effectively treated using low dosages of UV.
In the course of finding a solution for treating Cryptosporidium, the testing and research showed that at low doses,
UV would inactivate Cryptosporidium
and other similar parasites by preventing them from replicating and causing
infection. This was a major research achievement because UV's effectiveness
within this treatment range had not been previously demonstrated.
In fact all previous research, including that published
after Calgon Carbon's announcement, taught a conclusion contrary to that of the
Prior to announcing the results of the research, Calgon Carbon
filed for a patent covering the inactivation of Cryptosporidium and similar parasites at UV doses between 10 mJ/cm2
and 175 mJ/cm2. This patent was granted to the company in October 2000.
The scope of the patent essentially covers all usage of UV
technology in water treatment for the inactivation of Cryptosporidium and similar parasites.
In March 2002, the Canadian government also issued the
company a Notice of Patent Allowance. In early 2003, Calgon Carbon was granted
patents covering its inactivation treatment process in New Zealand and the
Netherlands. Finally, in May 2003, the company was granted its second U.S.
patent for preventing infection from Cryptosporidium and Giardia at UV doses of 1-175 mJ/cm2.
UV reactor validation
With the third-party testing and EPA's verification of
Calgon Carbon's breakthrough inactivation method complete, the company's
research efforts became focused on UV reactor validation to ensure water plant
operators of continuously effective levels of UV radiation.
Working with Carollo Engineers, Calgon Carbon assisted in
funding the first U.S. based UV validation facility in Portland, Ore. Within
months of completing the testing facility, validation testing was conducted on
the company's 48-in. Sentinel UV Disinfection System at flow rates of up to 40
million gallons of water per day (mgd), making this the largest UV validation
test ever conducted.
Prior to validating the Sentinel reactor, the largest
validated flow rate in the water industry was 18 mgd.
The Sentinel 48-in. UV Disinfection System was the first UV
reactor to be in compliance with the U.S. EPA's Microbial-Disinfectants and
Disinfection Byproducts Rules for the treatment of Cryptosporidium, Giardia and
other viruses in drinking water under the Long-Term 2 Enhanced Surface Drinking
Water Treatment Rule.
This large-scale validation process was a significant
advancement for the water treatment industry. For the 48-in. Sentinel to be
validated at 40 mgd was unprecedented, and such a system could offer cost
savings to municipalities and provide them with safe, high-quality drinking
Having complete control
Prior to Calgon Carbon's discovery, application of UV for
disinfection of drinking water, including complete control of bacteria,
viruses, and protozoa, was not considered an economically viable technology.
Many municipalities were considering expensive filtration
and ozone technologies that would have cost substantially more than the
Sentinel UV technology.
Since then, the water industry has been able to take
advantage of UV designs providing for more efficient and affordable
The final information required by state regulators to grant
disinfection credits for UV technologies is operational data. Calgon Carbon has
developed detailed guidelines and CDF modeling for design engineering issues.
Control and command features, system maintenance, and operator training are
based on the company's experience with over 250 UV installations treating
municipal wastewater, contaminated groundwater, industrial wastewater and