To:
Members, Affiliates, Pretreatment and Hazardous Waste Committee, and Mercury Workgroup
From:
National Office
Date:
August 14, 2000
Subject:
Evaulation of Domestic Sources of Mercury
Reference:
RA 00-16
In a new report released by AMSA, mercury levels in household wastewater are shown to be sufficiently high to pose Clean Water Act compliance problems for the nation's wastewater treatment plants. The findings of the AMSA study, developed by the Association's Mercury Workgroup, underscore the need for a comprehensive, priority-based, cost-effective national strategy to reduce mercury in the environment. The complete report, “Evaluation of Domestic Sources of Mercury,” can be downloaded by clicking on the link below.
Mercury contamination is the leading cause of fish advisories in the country. Because mercury bioaccumulates in the fatty tissues of fish and wildlife as it passes up the food chain, the U.S. Environmental Protection Agency (EPA) is expected to recommend significantly stricter national water quality criteria for mercury later this year — at or near the level of 1 part per trillion, which is already in place in the Great Lakes.
Many AMSA members are concerned that compliance will require the application of advanced treatment even though these kinds of costly controls may not have much impact on resolving water quality issues as long as mercury continues to enter the environment from other sources such as air pollution or abandoned mines. It is important to stress, however, that mercury from domestic wastewater and municipal treatment plants accounts for less than 1 percent of mercury entering the environment. EPA believes that by using new analytical and sampling techniques and pollution minimization, POTWs should have no difficulty in attaining these more stringent requirements. EPA's conclusions in large part are based on a 1994 mercury sampling project that showed four of nine wastewater treatment plants had non-detectable mercury levels. This approach, however, assumes that there is no background mercury concentration in domestic wastes. Until recently there has been very little information on mercury concentrations in domestic waste, mainly due to a lack of monitoring at a sufficiently low level.
To better understand the relative contributions of mercury in domestic wastes and potential source control options, AMSA initiated a study to collect information on concentrations of mercury in domestic wastewater, to identify the sources of mercury in domestic wastewater, and to evaluate the feasibility of controlling those mercury sources. Sources evaluated included common household products and food items, as well as research on mercury contributions from individuals with amalgam fillings. The results of this study offer some important observations for sources of mercury in domestic wastewater and the feasibility of effective control options. The major findings are listed below.
- Significant amounts of mercury at the average concentration of 138 parts per trillion were consistently found in strictly domestic wastewater in various parts of the country. This was wastewater that contained no industrial or commercial inputs, dental offices included. POTWs remove 99 percent of mercury that is discharged into sewage systems.
- Several common household and toiletry items were found to contain substantial concentrations of mercury when examined using sensitive analytical techniques. Although these products individually do not contribute significantly to a total concentration in wastewaters, their cumulative effect accounts for approximately 15 percent of the mercury concentration in domestic wastewater. The feasibility of controlling these sources would require a broad national effort.
- Although several sources contributing to the domestic mercury concentrations have been identified, human wastes (feces and urine) from individuals with dental amalgam fillings are believed to be the most significant source — greater than 80 percent. These results were corroborated by the results from chemical toilet and septic wastes that showed that a significant portion of the mercury in domestic wastewater is from uncontrollable sources such as dental amalgam fillings.
- While controlling human wastes is impractical, the long-term outlook is promising inasmuch as the trend in dental health is for fewer cavities and resulting in smaller and smaller populations of amalgam-loaded individuals over time.
- Based on this information, domestic waste contributes appreciable concentrations of mercury to POTW influent wastestreams and must be considered when addressing mercury control strategies and the likelihood of virtual elimination of mercury. Background mercury concentrations averaging more than 100 parts per trillion can be expected in POTW wastewater influents, even if complete elimination of industrial point source discharges is accomplished.
In EPA's cost analysis for the Great Lakes Water Quality Initiative, and in subsequent discussions with wastewater representatives, the Agency has supported the use of pollutant minimization programs as a way for achieving compliance. AMSA strongly endorses and promotes pollution minimization efforts, but is concerned that these efforts may not be adequate to produce the desired level of permit compliance sought by regulatory authorities, highlighting the need for a national mercury compliance strategy for POTWs. AMSA has promoted national permit compliance approach for mercury in its discussions with high level officials at U.S. EPA.
For more information on AMSA's Mercury Workgroup or to obtain additional copies of AMSA's Mercury report, please contact the AMSA National Office at 202/833-2672.
Attachment:
Evaluation of Domestic Sources of Mercury