Volume 43 Number 5
A History of Water & Microbiological Contaminants
Dr. John Snow, also known as the Father of Epidemiology, advanced this theory most notably following the famous Broad Street Pump incident in 1852. Snow realized from maps of the London area that cases of cholera were isolated to regions served by the Southwark and Vauxhall Company, using the lower Thames River as its water source and not in a neighboring section of the city served by the Lambeth Company, whose water came from the upper Thames. Removal of the Broad Street pump handle supplying water from the Southwark and Vauxhall Company was largely responsible for the cholera epidemic in the region. Several years later, Louis Pasteur defined the "germ theory" of disease, stating that infectious disease wasn't spontaneous but a result of the presence and/or growth of harmful microorganisms. By 1884, Robert Koch identified Vibrio cholerae as the causative agent of cholera.
Impact of water treatment
Although filtration was a great advance in water treatment practices in the early 20th century, the most significant advance was yet to come-chlorination. There's evidence of individual recognition of the benefit of disinfectants to improve water quality decades earlier, but it wasn't until around 1908 that public water works adopted the use of chlorine disinfectants. By 1941, 4,590 out of 5,372 public water works utilized chlorine disinfectants. Introduction of chlorine resulted in a 300 percent reduction of typhoid incidence-or the rate the epidemic was spreading. Eventually, chlorine disinfectants virtually eliminated typhoid, cholera and bacterial dysentery in the United States.
Water quality regulations
Other important water quality regulations include the Surface Water Treatment Rule or SWTR (1989), Disinfection By-Products (DBP) Rule (1992) and Groundwater Disinfectant Rule (2001). The SWTR requires that public water systems utilizing a surface water source must achieve at least a 3 and 4 log removal or inactivation of Giardia and viruses, respectively. Recent modifications to this include the Enhanced SWTR, Long Term 1 SWTR and Long Term 2 SWTR. The DBP Rule is aimed at reducing allowable limits of total trihalomethanes (TTHMs), the precursors to harmful DBPs. The Groundwater Disinfectant Rule requires that all utilities using groundwater as a drinking water source disinfect or develop criteria to demonstrate a low probability of microbial contamination.
Evolution of disease
We recognize now that waterborne disease symptoms extend far beyond diarrhea and may include diabetes, autoimmune disorders, arthritis, cancer, birth defects and diseases of the liver, kidney and heart. While these sequelae-a diseased condition following and usually resulting from a previous disease-may not be immediately life threatening, one's quality of life can be greatly affected. Likewise, the cost burden to society is immense due to chronic illnesses. Another factor to consider is the growing population of immunocompromised individuals-both because of aging populations and emerging diseases such as AIDS. These sensitive populations are more susceptible to waterborne infections and tend to experience a more severe outcome (i.e., serious illness, death) following infection. Adverse health conditions continue even with use of state-of-the-art treatment plants and many regulatory efforts to improve water quality. This is where point-of-use (POU) treatment options can have a dramatic impact.
For all of the benefits that filtration and disinfectants can claim regarding water quality, we're at a point where the definition of acceptable water quality is changing. Improvements in and increased monitoring reveals up to 39 percent of finished waters in the United States are contaminated with viruses or parasites1,2. In addition, research has recently revealed protozoan pathogens (i.e., Cryptosporidium) are highly resistant to chlorine inactivation, requiring a ct value (concentration of disinfectant vs. contact time) of >7,200 compared to a ct value of 0.04 for enteric-or intestinal-bacteria.
Treatment at the tap?
About the author
August 1998: Guidance on variance technologies for systems serving less than 10,000 people -- Small systems may use POU/POE devices to meet regulations on contaminants. Devices must be owned by utilities or persons under contract to utilities.
August 1998: Consumer Confidence Reports -- Requires utilities to send each of their customers an annual report that tells where they get their water, how it's treated and what's detected. First report required by October 1999.
November 1998: Stage I Disinfectants and Disinfectant Rule -- Sets standards on use of disinfectants and disinfection by-products (DBPs).
November 1998: Interim Enhanced Surface Treatment Rule -- Designed to a set treatment standards to reduce risk from Cryptosporidium.
1998 - 2001: Waterborne Disease Occurrence Studies -- Requires EPA to conduct epidemiological studies to determine how much waterborne microbial disease occurs in the U.S.
1998: Sulfate Study -- Requires Centers for Disease Control to conduct studies on sulfates to develop standards.
April 1999: Information Collection Rule (ICR) -- First data become available on a nationwide survey on occurrence of viruses, Cryptosporidium, and DBPs in drinking water.
August 1999: Proposed Radon Standard -- EPA is correctly developing a database for standards. Utilities in Wisconsin and Illinois would be most impacted.
Jan. 1, 2000: Proposed Arsenic Standard -- Cost and benefit analysis drew out debate on whether to lower from 50 ppb to 5 ppb or 10 ppb (matching the World Health Organization guidance on this contaminant); January 2001 decision by Clinton Administration to set it at 10 ppb was withdrawn for review by Bush Administration in March 2001.
November 2000: Final Enhanced Surface Water Treatment Rule -- The results of the ICR database will be used for a final treatment rule to control Cryptosporidium, viruses, and DBPs.
May 2001: Groundwater Rule -- Rules requiring disinfection of all public water supplies that use groundwater.
August 2001: Determine whether to regulate at least some contaminants from Contaminant Candidate List (CCL) -- Awaiting action.