Ozone technology developments have opened new applications for these established water treatment technologies. Driving these changes has been the identification of new, more disinfection-resistant microorganisms such as Giardia and Cryptosporidium cysts and governmental regulations designed to protect the public health from the hazards of ingestion of these microorganisms. Additionally, the desire to prevent or minimize the formation of halogenated disinfection byproducts formed during chlorination has stimulated new interest in the use of ozone. Combinations of ozone with hydrogen peroxide and/or ultraviolet (UV) radiation can destroy many contaminants present in ground water.
Small Systems Adopt Ozone Technology to Protect Against Cryptosporidium, Giardia
Editor’s Note: Part 1 of this series provided a timeline for the development of a drinking water standard for arsenic. It also summarized the political and public reactions to the U.S. EPA decision to delay and withdraw the arsenic rule.
Part 2 dealt with human exposure and advances in knowledge concerning human health effects of exposure to arsenic.
Part 3 summarized early data on the occurrence of arsenic in U.S. waters.
Arsenic Removal Methods
Only recently has a substantial amount of data become available on the concentrations of arsenic in United States drinking water supplies. Most of these data have been accumulated by the state regulatory agencies responsible for monitoring drinking waters. Since the arsenic standard has been 50 µg/L, some state agencies have recorded arsenic concentrations only in excess of that concentration. Others have been limited by the sensitivity of the analytical techniques and equipment used for the arsenic analysis. As a result, much of the available arsenic data are “below the limits of detection.
Occurrence of Arsenic in U.S. Waters
Metals such as bronze, copper and iron have been used for thousands of years by man for both peaceful and non-peaceful purposes. One of the most useful purposes for metal is the production of steel.
On November 26, 2001, the new arsenic standard was signed into law—lowering the acceptable level for the contaminant from 50 parts per billion (ppb) to 10 ppb. Approximately 4,100 municipal water systems serving nearly 13 million people nationwide are affected by the law and are required to meet compliance by January 2006. According to the U.S. Environmental Protection Agency (EPA), 97 percent of these systems are small systems serving fewer than 10,000 people each. The economic impact on these small systems is likely to be large. However, there currently are options available to small municipalities that may be more affordable than central treatment.
New POU Technologies May Be the Answer for Small Municipalities Facing High Costs
On-going health effects studies and research reports (2001) appear to support the argument for lowering the current EPA drinking water standard for arsenic. Studies conducted by EPA, the University of North Carolina and the University of British Columbia have indicated that methylated metabolites of trivalent arsenic are genotoxic. In other words, they damage DNA in human cells.
Human Exposure and Health Effects
Purification of drinking water containing microbiological contamination requires some form of disinfection treatment to kill or render microbiological organisms harmless.
Of the available disinfection treatment methods for private water systems, chlorination in the most commonly used.
A disinfection choice for public and private water systems.
In March 2001, the U.S. Environmental Protection Agency (EPA) withdrew a proposal for a lower maximum contaminant level (MCL) for arsenic in drinking water that would bring the standard from 50 parts per billion (ppb) to 10 ppb. At that time, the EPA commissioned three studies to examine the benefits, costs and health effects associated with a lower standard for arsenic.
A brief look at one solution for arsenic removal
Recent market research showed that more than 73 percent of consumers prefer to consult with a water treatment professional when dealing with arsenic. Combining this inclination with the preference for the POE approach, the treatment professional has a unique opportunity to generate significant new revenue from POE sales with minimal upfront effort.
The National Academy of Sciences, National Research Council (NAS-NRC) report was released on September 11, 2001. It concluded that the existing health effects data on arsenic essentially were sound. In addition, their review of three new epidemiological studies indicated that the health risks posed by arsenic in drinking water were greater than previously believed. As a result, in October, well before its self-imposed deadline, EPA rescinded its March implementation ban and endorsed the 10 µg/L arsenic MCL.
The Development of Drinking Water Regulations