By Jack Adams and Leo Zappa
Recent events such as the Elk River chemical spill in West Virginia, Lake Erie algal bloom and historic drought gripping the West splash across the headlines. The Environmental Protection Agency (EPA) and state environmental agencies are working to limit the formation of disinfection byproducts in our drinking water, runoff of agricultural chemicals into our water supplies and increasing prevalence of pharmaceuticals, personal care products and other chemicals of emerging concern in our waters. These events illustrate the vulnerability of our drinking water supply and infrastructure.
More than 200 million Americans receive their drinking water from nearly 12,000 community water systems that withdraw source water from nearby rivers, streams and lakes, which are often located near industrial facilities such as factories and storage tanks, rails and roadways, as well as hospitals and other healthcare facilities. Many of these waterways are also used for recreation and to transport chemicals and other commodities.
Accidents and unintended consequences do happen -- and when they do, the potential exists for contamination. There is great interest on the parts of water utility management, state and federal regulators, elected officials, and the general public to provide an effective barrier that will protect drinking water supplies when accidents occur and from the unintended consequences of chemical use.
Barrier Technologies for Accident Protection
Drinking water treatment facilities typically have little to no warning when accidents threaten their operations. Frequently, these facilities are notified only after the contamination has already reached the plant's intakes and been drawn into the infrastructure. This places the consuming public at risk and often disrupts the water supply until the threat passes and the water treatment infrastructure can be cleaned.
One strategy to avoid these risks is to implement "barrier" technologies that prevent unwanted chemicals from entering the water distribution system as well as homes and businesses.
Most drinking water treatment plants in the U.S. are of the "conventional" design, consisting of flocculation, coagulation, sedimentation, particulate filtration, and final disinfection processes. While this design has proved effective over the years for the treatment of organic compounds ordinarily found in surface water, it may not be effective when faced with the often complex and sometimes exotic chemicals released from accidents or chemicals of emerging concern.
To prevent water treatment plants from discharging tainted water into their distribution systems, additional "barrier" technologies may be required. Examples include adsorbents (e.g., granular activated carbon), membranes (e.g., nanofiltration, reverse osmosis [RO], ultrafiltration), and oxidation (e.g., ozone, peroxide). In fact, these technologies are already in use in some drinking water treatment plants as part of the normal operation of those facilities.
Barrier Technologies for Unintended Consequences
One of the most significant innovations of the 20th century was broad use of disinfection practices. These practices -- and their associated technologies -- for drinking water destroyed biological organisms that caused widespread disease and death. The public health benefits of drinking water disinfection with chlorine and other oxidizing chemicals are unquestionable.
More recently, however, it has been discovered that the reaction of disinfection chemicals with naturally occurring and other materials in source water can form undesirable chemicals grouped as "disinfection byproducts." EPA now regulates the distribution of a targeted list of these chemicals under their Stage 2 Disinfectants and Disinfection Byproduct Rule. Some utilities have elected to use chloramines for disinfection to avoid the formation of regulated disinfection byproducts. However, chloramines can often form unregulated disinfection byproducts that are even more toxic.
Various barrier technologies can remove the naturally occurring and other materials prior to the disinfection step in drinking water processing, thereby reducing or eliminating the chemical reaction that forms disinfection byproducts. Alternatively, barrier technologies can be used at the end of the treatment process to remove the formed byproducts prior to distribution.
As with disinfection practices, advances in healthcare and pharmaceutical science provide significant healthcare benefits. However, the accumulation of these chemicals in our drinking water works counter to their intended benefit. An effective barrier technology can remove this unintended consequence.
About the Authors: Jack Adams is director-Government Affairs at Calgon Carbon Corporation and is a member of the board of directors of the Water and Wastewater Equipment Manufacturers Association (WWEMA). Leo Zappa is marketing director, Municipal Business Unit, at Calgon Carbon Corporation.
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