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Mercury
Work Group
Phase I Reports >> End of Pipe Report
Executive Summary | End-of-Pipe Report |
Operations Report | Infrastructure Report
For more information,
contact David Eppstein by email at
deppstein@masco.harvard.edu,
or by calling 617-632-2860.
Wastewater
Characterization
In order to help evaluate
various technologies and to answer the equipment supplier's
questions, the Subcommittee needed to establish how much mercury
its members were currently discharging to the MWRA Sewerage
system. Initially, the Subcommittee prepared and issued a
questionnaire to its members which requested this information
plus asked for information regarding what other pollutants or
constituents might be contained in the wastewater being
discharge from their facilities. Since most of the membership
did not have this type of information readily available, the
Subcommittee received only a very nominal response. A summary of
the information which was received, however, is presented in the
attached Table entitled Historical
Wastewater Characteristics.
As a next step in this
process, the MWRA was asked and agreed to implement
"Special Sampling" at a number of Member Institutions
in order to produce the information required by the Subcommittee
for subsequent evaluation. A summary of the results obtained via
this "Special Sampling" is presented in the attached
Table entitled "Special
Sampling" Wastewater Characteristics.
The information
provided in these Tables represents only a small segment of the
member institutions. However, the data does reflect that a
significant amount of material other than mercury is discharged
from these facilities which would significantly and adversely
impact of any form of end-of-pipe pretreatment process if not
individually addressed. The data also represents a cross section
of the Member Institutions in that data was generated from
facilities discharging from a low of 500 gallons per day
(small), through a mid range of 3,000 to 10,000 gpd (medium), to
some of the larger institutions which discharge upwards of
20,000 gpd through a single discharge location. The data
indicates that, regardless of flowrate, each wastestream
produced in a combination of clinical and research laboratories,
contains organic material (BOD), heavy metals, traces of organic
solvents and conventional pollutants (oil/grease, solids,
nutrients, pH) all mixed in with trace levels of mercury.
This characterization
data certainly posed a dilemma to most vendors in that in order
to access the main target - mercury, the entire wastestream
would have to be cleaned of all contaminants, whether or not
regulated. Copies of this characterization data were issued to
all vendors making presentations to the Subcommittee for
consideration and in preparing definitive recommendations for
how their technologies might be able to be adapted for use in
meeting the mercury challenge.
Realizing that the data
base regarding levels of mercury being discharged to the MWRA by
our membership was thin, the Subcommittee asked the MWRA for
historical information contained in their records. In response,
we received a statement of mercury discharged, by Institution
and discharge location within each institution, and the flowrate
at each discharge point for the period January 1, 1993 through
April 15, 1995. Our Subcommittee subsequently broke this data
down into three parts since we realized that certain progress on
mercury abatement via operational changes/source control
procedures and infrastructure maintenance had been made over the
course of the overall Workgroup's involvement on this issue.
Accordingly, we placed all information available in the database
prior to July 1, 1994 into a spreadsheet called Review
of SMART Database, Fiscal, 1994 in an effort to
establish the levels of mercury being discharged to the MWRA
sewerage system by our members before they gained a full
appreciation of the problem. It also seems that during this
period, the MWRA did not fully have an understanding of the
problem since the number of data points available, and the
number of institutions required to analyze for mercury, was not
as great as compared to subsequent periods of review.
Next, we entered all
data available for the period July 1, 1994 through December 31,
1994 into the next spreadsheet because it seemed that a
significant amount of progress was being made during this period
by each facility in cleaning out traps, powerwashing piping and
tanks, and generally educating their staff about the problems
associated with discharging mercury bearing wastes to the lab
sinks which would ultimately end of in the sewer. This
information, which contains a significantly greater number of
data points and thereby provides a greater level of confidence
in data interpretation, is still believed to be somewhat
misleading in reflecting the actual and current situation
relative to mercury discharges from the Hospital community to
the MWRA sewerage system in June of 1995. The results of our
second data entry effort is presented in the attached
spreadsheet entitled, Review of
SMART Database, Q1& Q2, Fiscal, 1995.
Finally, relative to
the raw database, we entered the most current information for
the period January 1, 1995 through April 15, 1995 into the final
spreadsheet so we could determine what the impact of our efforts
at mercury concentration reductions within individual facilities
had made. Further and, more importantly, we wanted to estimate
the aggregate mass of mercury being discharged to the MWRA
sewerage system by the total membership of the Hospital Mercury
Workgroup since education on this issue began. The results of
our third data entry effort is presented in the attached
spreadsheet entitled, Review of
SMART Database, Q3 & Q4, Fiscal, 1995.
These individual
tabulations of the raw SMART database seem to indicate a certain
level of improvement in the overall quality of the wastewater
being discharge by the Mercury Workgroup membership over the
period of review, which was expected. However, the data, in our
view, is still somewhat misleading for two reasons:
1. stated flows at each
discharge location were estimates provided by each Institute
based on an incorrect facility water balance of historical water
meter readings, and
2. data tabulations do
not recognize "non detects" of mercury analysis as 0.0
ppb.
The next iteration of
the database attempts to correct these artificially high
results.
It seems, in most
cases, and without any particular basis, that facilities would
tend to overestimate the amount of wastewater they would
discharge through their "special waste" systems and on
to the MWRA sewerage system. Recent education on this front,
have caused certain members to install in-line flow meters at
their discharge points so as to establish actual flow rates to
the MWRA sewerage system. Though many installations are
underway, only a few meters have recently been installed and are
now operating. Where current information on flow is available
from these limited installations, it has been entered into the
database in the fourth spreadsheet entitled, Review
of SMART Database, Q1 & Q2, Fiscal, 1995, after removing ND
results and substituting actual flow from meters, where
installed. Note that, due to the greater
number of monitoring data points available and therefore the
greater level of confidence in the database, the data compiled
for Q1 & Q2, Fiscal, 1995 was used for this demonstration.
The final spreadsheet,
SMART Data Summary,
provides a summary of information presented in more detail in
the preceding data tabulations but certainly illustrates the
progress that has been made by the membership over the past year
in addressing the overall mercury problem. This summary seems to
indicate, without benefit of database correction for flow or
ND's on mercury analysis, that there has been a 70% reduction in
the total mass of mercury being discharged into the MWRA
sewerage system as a whole (2.36 to 0.47 ounces per day), and
that the average discharge concentration of mercury coming from
the membership has been similarly reduced by more than 80
percent during the same period (21.4 to 4.3 ppb). Notably, only 15%
of the 76 recorded discharge locations currently remain at
concentration levels that exceed the aggregate membership
average of 4.3 ppb while nearly 80% remain at levels in
excess of the MWRA stipulated enforcement threshold of 1.0 ppb.
Interpretation of the
data after substituting current flow information and removing
analytical NDs yields an even more positive measure of
performance. The aggregate mass of mercury being discharged by
the Membership is reduced by 87% to only 0.31 ounces per
day which translates to an average concentration of 2.5 ppb.
Though the percentage of discharge points in excess of this
average remains at 13%, the number of discharge points in excess
of the 1 ppb discharge standard drops from 48% to 33%.
Clearly this data is significant and demonstrates the dramatic
impact that source reduction and infrastructure measures have
had upon the overall mercury discharge issue. Though this
finding bodes well for the Membership at large, the unsettling
piece of information derived from this review, at least from the
End of Pipe Subcommittee's perspective, however, is that the
influent mercury concentration available to the pretreatment
technologies we were charged with investigating, has already
been reduced to levels below that which has been demonstrated as
attainable by the pretreatment equipment via actual field
trials.
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