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Mercury
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Phase II Reports >> Facilities Loadings
Facilities Loadings
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For more
information, contact David Eppstein by email at
deppstein@masco.harvard.edu,
or by calling 617-632-2860.
1.0 EXECUTIVE SUMMARY
In its June 1995 report, the End-of-Pipe Alternatives Subcommittee in
Phase I of the MWRA/MASCO Mercury Work Group concluded that 29 local hospitals discharged
approximately 2 percent of the total daily mass loading of mercury to the MWRA sewer
system of the Boston Metropolitan Service Area. The loadings estimate of the MWRA itself
was higher because of different assumptions and data. In an effort to better understand
the mercury loadings contributed by these and other similar dischargers, the Facilities
Loadings Subgroup of the Mercury Management Subcommittee was formed in 1996 under Phase II
of the MWRA/MASCO Mercury Work Group.
The goal of the Facilities Loadings Subgroup was to estimate known and
projected mercury loadings to the MWRA Metropolitan Boston sewer system contributed by
hospital and medical facilities over a two-year period. The Subgroup was also asked to
reexamine the mercury loadings contributed by the 29 local hospitals studied in Phase I.
The Subgroup decided to examine five study groups of hospital-like
facilities as follows: clinical laboratories, medical waste incinerators, hospital
laundries, other related facilities (including college laboratories, steam suppliers,
pharmaceutical manufacturers, and testing laboratories), and medical and biotech research
laboratories. From a list of all MWRA permitted facilities, the Subgroup found 242 of
these facilities and further determined that these facilities had a total of 355
qualifying permitted discharges or sampling locations.
We found that the sampling locations of the five study groups made
significant contributions of mercury to the sewer system. We estimated that, collectively,
they contributed about 50 percent of the known daily industrial mercury loadings during
the two-year study period. Yet, these sampling locations discharged only about 16 percent
of the estimated total daily industrial discharge flow. We also estimated that their
combined mercury loadings represented about 6 or 7 percent of total mercury loadings to
the sewer system while their discharge flows were only about 0.5 percent of the total
treatment plant headworks flow. However, since these results are based upon a limited
amount of data, we advise appropriate caution in their use.
On an individual basis, we found that a typical medical waste
incinerator discharged the highest mercury loadings followed by a typical medical and
biotech research laboratory. In contrast, we found that a typical clinical laboratory
discharged relatively high mercury concentrations but relatively low mercury loadings
because of its lower discharge flows.
In Phase I of the Work Group, the End-of-Pipe Alternatives Subcommittee
had estimated that the mercury discharge loadings from 29 local hospital facilities
represented between 2.6 and 3.6 percent of MWRA total system loadings during the MWRA 1995
fiscal year (FY). In this new study, our results instead suggest that the FY 1995 loadings
contribution from these facilities may have been between 0.6 and 0.9 percent. For FY 1996,
we estimate that their loadings contribution may have been between 1.8 and 2.5 percent of
MWRA total system loadings.
Finally, we found that the total average mercury loadings discharged
from the five study groups may have been between 0.02 and 0.08 pounds per day over the
study period. Since this sum represents such a small quantity of mercury, one sporadic
peak discharge had the potential to significantly affect the overall loadings for a
particular day.1 We observed such sporadic impacts in the discharge
concentration data over the two-year study period for sampling locations within several
clinical laboratory, medical waste incinerator, hospital laundry, and research laboratory
facilities. During FY 1995, for example, the data suggests that a research laboratory may
have discharged 0.24 pounds of mercury in one day and, during FY 1996, a hospital laundry
may have discharged 0.11 pounds of mercury in one day.
1Readers of
this report are encouraged to refer to the Work Group's Mercury Management Plan Guidance
Document for recommended guidelines to address mercury management issues including the
control of sporadic high mercury discharges.
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