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Water Quality | Mercury
Mercury and Wastewater Treatment Facilities
Mercury that is discharged from wastewater treatment facilities can originate from the industrial, commercial, and residential sources that contribute to the facility, but it can also come from the facility itself. Potential sources of mercury from facilities include laboratory equipment, laboratory chemicals, bulk chemicals, process control and measuring equipment, lamps, batteries, paint, and first aid/medical equipment. Some mercury-containing items may be replaced with non-mercury alternatives while some items can continue to be used, but should be recycled properly. The Delta Institute, a nonprofit organization that engages in the policy and practice of improving environmental quality and promoting community and economic development, has developed a Mercury Checklist for Sewage Treatment Plants that lists all items that may contain mercury at wastewater treatment facilities.
Mercury is found in wastewater from industrial, commercial, and residential sources, but dental offices have been found to be a significant source of the mercury that reaches wastewater treatment facilities. Dentists are the third largest users of mercury in the United States. The Massachusetts Water Resources Authority estimated that dentists contribute at least 10% of the mercury in their treatment plant. Previous studies estimated that the contribution of dentists is 8 to 13% in San Francisco, 14% in Seattle, and 26% in Duluth. Many dentists use amalgam, containing approximately 49% mercury, for fillings and studies have shown that about 54% of the amalgam mixed for fillings ends up as waste. The American Dental Association has developed Best Management Practices for Amalgam Waste to reduce the amount of mercury entering the waste stream.
The Association of Metropolitan Sewerage Agencies’ (AMSA) 2000 report, Evaluation of Domestic Sources of Mercury (http://www.amsa-cleanwater.org/pubs/mercury/mercury.pdf) estimates the mercury contributions from human waste and household products. The study found that human wastes from individuals with amalgam fillings are the most significant sources of domestic mercury, and make up about 80% of domestic mercury. A number of common household, food, and toiletry products, such as dishwasher detergent, fruit juice, and laundry detergent, were found to contain substantial concentrations of mercury. The cumulative contributions of these sources make up about 15% of the mercury concentration in domestic wastewater.
For more information about mercury, contact Susy King, our mercury coordinator.