The Washington County Lead District is located in Washington County, MO approximately 100 miles south-west of St Louis. The EPA has been conducting Removal Assessment and Removal Action activities in Washington County since 2005. Most of the sites identified within Washington County consist of residential properties contaminated with lead and other heavy metals from former mining operations conducted in the region. Contamination is commonly found in soils and drinking water wells. There are several sites located within the Washington County Lead District. These sites include; Potosi, Old Mines, Richwoods, Furnace Creek, Palmer, and Pea Ridge. Most of these sites include contaminated properties with both soil and drinking water contamination. Where contaminated drinking water have been identified, an alternative water provision is provided to residents by the EPA. In most cases, this has been accomplished by the delivery of bottled water to the resident on a monthly basis.
The EPA is now conducting a pilot study to investigate a more permanent solution for the treatment of contaminated wells in Washington County. Point-of-Use (POU) filtration units are currently being tested to determine if the POU technology is appropriate for the Washinton County sites. A pilot study utilizing several types of POU systems was started in December of 2010. The Study will continue through fiscal year 2012 at which time a permanent treatment technology will be selected to address contaminated wells within Washington County.
Several types of POU units were selected for the pilot. Each system will be sampled on a quarterly basis throughout the study. In addition to wells contaminated with lead, a small number of properties in Washington County were identified with cadmium contamination. Water treatment at these properties will be tested utilizing reverse osmosis POU systems. All of the POU systems will be evaluated for their functionality, reliability to successfully remove contaminants, and overall satisfaction reported by the resident.
The EPA has installed both types of systems in homes for various types of drinking water contamination. Whole-house filters have been considered for the Washington County site and are also currently are being reviewed. The lack of space within smaller homes and trailers may prevent the installation of larger whole-house units. The increased maintenance costs of these systems may also be a significant burden on home owners.
Whole-house treatment units typically are installed for wells contaminated with Volatile Organic Compounds (VOCs) to address all water usage in the home. Since the pathway of highest concern for lead contamination in water is through ingestion, there is reduced concern that exposure will occur through volatilization and inhalation while residents are using showers, baths, and cleaning and washing activities. Water treatment systems for lead contamination can be limited to only locations where water will be consumed.
An initial review of domestic water treatment technologies was conducted in a study titled "Sampling and analysis of Household Well Water in Mine Waste Areas and Selection of Point-of-Use Treatment Devices" prepared for the EPA by Shaw Environmental, Inc. (Shaw, April 2010). Carbon-based filter technology was determined by this study as the most effective filter system for removing lead contamination from drinking water at the POU. The study reviewed several types of POU filters including Solid Activated Block Carbon filtration (SBAC), reverse osmosis, and atomic adsorption. SBAC was selected for it’s effectiveness at removing lead contamination, it’s ease of use and modest installation and maintenance costs.
In addition to the treatment of lead contaminated wells, a small number of wells within Washington County have been identified with cadmium contamination. These properties represent a small fraction of the number of contaminated wells within the County (a total of eleven out of 254 contaminated wells in Washington County have cadmium contamination above the MCL). Wells contaminated with cadmium will required reverse osmosis (RO) filtration systems for treatment. Although SBAC has been successful in removing cadmium contamination in some circumstances, SBAC filters are not certified by the National Sanitary Foundation (NSF) for the treatment of cadmium. During testing conducted during the POU Study, it was observed that cadmium breakthrough in SBAC filters consistantly occured when untreated water contained cadmium concentrations above 20 parts per billion (ppb). Due to this limitation with SBAC, reverse osmosis (RO) filtration units will be utilized for all properties identified with cadmium contamination. The RO units will also be evaluated for overall performance and functionality.
In December 2010, SBAC or RO systems were installed in 28 properties at sites within Washington County. Additional system installation is currently under way. Initial sampling of the systems was completed in February 2011. Each system will be sampled once per quarter until the second quarter of fiscal year 2012. Sampling of these systems and overall resident surveys will be conducted to determine which system is most effective and reliable for future use. The systems were installed in several different configurations. In general, SBAC systems were installed with a 1.5 gallon per minute filter feeding a 2-3 gallon accumulator tank. Depending on water pressure levels within the home, some systems were installed with booster pumps to increase flow rate through the filter. Since RO systems produce water at a much slower rate than SBAC, about 1 gallon every 30 minutes, the majority of RO systems were installed with booster pumps. All systems were installed with a digital monitor to record total gallons produced and flow rate.
Additional systems may be installed in the coming months as properties are identified with contaminated wells. It is anticipated that the review of filtration units will be completed by the end of 2011. Selection and installation of a permanent alternative water technology will be made at that time.
Monitoring of the filtration systems will continue through FY2012. Additional research and assessment will be conducted to determine other technologies for treating lead contaminated wells during this time as well. A final report will be submitted describing the performance of the units throughout the pilot study. Comments and complaints from residents will also be noted to determine if the system will likely be rejected by property owners due to significant maintenance burden or for usability and performance reasons.
It is anticipated that additional systems will be installed as additional requests for filters are sent to the EPA or until a permanent solution is determined by EPAs Remedial Program. Adjustments and changes will be made to the systems throughout the study as needed. All changes to the systems will be recorded and included in a final report to be submitted after the study is complete.
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