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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.
9.0 COMMENTS AND CONCLUSIONS
We believe we have fully met the goals of our Phase II task and have
produced several mercury discharge loadings estimates for five groups of facilities with
hospital-like sewer discharges. To aid in the evaluation of our study results, we have
also provided several comparisons of our estimates with total industrial loadings and
sewer system loadings. However, since the results of this study are based upon a limited
amount of data, we advise appropriate caution in their use.
Although we are confident that our laboratory discharge flow model has
produced good estimates of discharge flows on an overall basis, we are not as confident in
our calculated mercury concentration averages for all sampling locations. We believe that
additional testing at many existing sampling locations would lead to better estimates of
average discharge mercury concentrations. Additional concentration data would also help
individual facilities to better understand their mercury discharge position. On the other
hand, since discharges having large flows usually had permit sampling requirements, 60 to
70 percent of our estimated total mercury loadings were contributed by locations having
actual concentration data.
For sampling locations that had outliers in mercury concentration test
data, we believe that causes of the outliers should be determined on a case-by-case basis
so that any needed adjustments to the record can be made. In addition, we believe that the
installation and calibration of wastewater flow meters at more sampling locations would
lead to better discharge flow information than was available for this study.
Even with the necessary assumptions and approximations, we believe that
this study provides important insights into the sewer discharge mercury loadings
contributed by our five study groups. Specifically:
During FY 1995 and FY 1996, our five study groups contributed roughly
50 percent of the known industrial mercury loadings while discharging only about 16
percent of the estimated total industrial discharge flow to the Boston Metropolitan Sewer
Service Area.
During this period, our five study groups contributed roughly 6 or 7
percent of total headworks mercury loadings while discharging only about 0.5 percent of
the total treatment plant headworks flow.
On a group basis, research facilities appeared to be the largest
contributors of discharge mercury loadings. However, this result could have been expected
since there were 193 research sampling locations out of 355 sampling locations examined in
this study. Also, during one half-year period in FY 1996, laundry facilities were
significant contributors of mercury loadings because of one laundry sampling location with
a very high loading.
On an individual basis, a typical incinerator facility had the
greatest potential to be a large contributor of discharge mercury loadings followed by a
typical research facility. Although a typical clinical facility had the potential of
relatively high discharge mercury concentrations (see the Group Concentration Averages
in Tables 1 and 2), its mercury loadings would be relatively low because of lower
discharge flows.
The Phase I End-of-Pipe Alternatives Subcommittee had estimated that
the mercury discharges loadings from 29 selected hospital facilities represented between
2.6 and 3.6 percent of MWRA total system loadings during FY 1995. In contrast, our results
suggest that the contribution from these facilities was between 0.6 and 0.9 percent for FY
1995 and between 1.8 and 2.5 percent in FY 1996.
We also 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.8 We observed such sporadic impacts in the discharge concentration data
over the two-year study period for sampling locations in 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.
8Readers 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
psoradic high mercury discharges.
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