|
Mercury
Work Group
Phase I Reports >> Infrastructure 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.
5.0 SPECIAL WASTE RISER
The "Special Waste" riser diagrams are an important
tool in approaching wastewater compliance for mercury. The riser
diagram illustrates to regulating authorities (MWRA) that an institution
has extensive knowledge and control of all special waste discharges.
The diagram will indicate areas of inability to control and isolate
special waste discharges for all "Special Waste" sources.
As required by the Massachusetts State Plumbing Code, 248 CMR
2.13 (12/1/93), all plans and specifications for "Special
Waste" piping and pretreatment systems shall be prepared
by a Registered Professional Engineer.
The inability to contain and isolate the discharge of mercury
or other non-compliant wastes into the public sewer system is,
in large part, due to the indiscriminate routing of "Special
Waste" piping systems, their interconnections with each other,
lack of future planning and restrictive economic considerations.
The proposed use of isolation valves in "Special Waste"
and vent piping systems under 248 CMR 2.05 (12/1/93), is allowable
when the valve would not cause a normal frictional obstruction
to flow in the piping system or when the valve has "a desirable
and acceptable function and as of the ultimate benefit to the
proper and continuing function of the plumbing system."
The ability of the isolation valves to allow for trap cleaning,
removal of non-compliant wastes, sampling or suspect branch piping
and control of waste flow from cross-contaminating the entire
special waste piping system would be allowable. However, each
proposed installation must have the approval of the local plumbing
inspector and each location, when installed with a sampling port,
must be approved by the MWRA or the DEP.
The Infrastructure Committee recommends that the following guidelines
be followed when planning to install or modify an existing piping
system capable of having isolated trap and pipe cleaning procedures:
An on-site audit of existing piping systems should be conducted
and drawings prepared to reflect the actual waste, vent, and associated
pretreatment system installations. Figure 5.1 is an example of
a "Special Waste" riser diagram prepared by Beth Israel
Hospital. This diagram illustrates individual floors and sinks,
with each individual sink identification number, and stack color
code and numbering system. An exploded view of a typical "Special
Waste" and vent riser diagram is shown in figure 5.2. This
diagram displays strategically located isolation ball valves,
glass inspection pieces, and sampling/drain valves.
System designs or modifications to an existing system in order
to allow isolation of wastes for cleaning, testing, etc., must
take into account:
- The type of wastes being discharged and the piping material
compatibility.
- The future use of laboratory spaces (i.e., chemical changing
to blood lab).
- The need to isolate branch piping from waste and vent stacks
to allow piping cleaning without the potential of constricting
waste flows from other areas or causing overflows to other uncontaminated
piping systems.
- Caution should be taken when combining any unidentified "Special
Waste" piping to previously identified "Special Waste"
systems. All waste sources and piping should be investigated
for biomass and mercury content prior to combining with previously
identified piping. Pending the results of investigation of these
new sources, additional isolation valving and/or new dedicated
risers to the neutralization system may need to be installed.
The location of isolation valves for cleaning or flow control
must be placed with consideration for accessibility and maintenance
especially when co-fitted with a sampling port for testing. An
example of suggested isolation valve locations is shown in figure
5.2. The location of valves cannot cause an overflow of non-compliant
wastes into another area where a spill may occur. As an example,
a floor drain would overflow if too much sanitizing liquid used
for the pipe cleaning procedure was poured into a countertop sink
situated at a higher elevation. Additionally, the need to provide
isolation valves in the venting system must not be overlooked
for the same reasons.
The sampling port may act as not only a testing point, but also
a drain leg for the isolated sanitizing and cleaning agents used
in the affected branch of piping. The serrated nozzle may be
replaced with a full-size drain leg for the transfer of suspected
non-compliant wastes to a container for off-site disposal. See
Figure 5.2 for typical locations of sampling/drain valves.
Figure 5.1 Typical "Special Waste" Riser
Diagram
of Beth Israel Hospital
Source: Beth Israel Hospital, Boston, Facility Engineering Department
Figure 5.2 Typical "Special Waste" and Venting Riser
Diagram
Source: Flow Tech Associates, Inc., Detail 1B
Vertical "Special Waste" and vent piping risers may
need to be isolated in order to allow for sequential cleaning,
sanitizing and testing of portions of entire systems in the same
manner as has been explained for horizontal runs of piping. During
these periods, special consideration must be given to the isolation
of vent piping due to the potential for overflow of reagents back
through the piping system.
A section of clear borosilicate glass piping should be installed
within the main horizontal run of the "Special Waste"
conveyance system employing thermo-plastic piping so that flow
conditions can be viewed and the formation of biomass accumulation
can be periodically observed. Figure 5.2 presents a suggested
location for this glass inspection piece. If branch piping containing
undiluted hydrofluoric acids is being used, however, this piping
should be routed separately and connected downstream of the glass
piping and fitted with its own isolation valve and sampling port
assembly.
The type of sanitant and cleaning agent being used must be analyzed
in conjunction with what may be contained in the piping system
from a chemical interaction perspective.
The potential for incompatible reactions should be considered
to ensure that trap and pipe cleaning procedures will not create
an unsafe condition. Reactions that may cause fuming and result
in gas generation into the working environment, as well as into
the piping system, must be avoided.
All proposed special waste piping and pretreatment installations,
modifications, revisions and additions must be detailed in engineering
drawings and specifications certified for 248 CMR 2.0 (12/3/93)
compliance (unless otherwise noted as an alternate design) and
must be submitted to the local Plumbing Inspector for review and
approval prior to construction. These approved documents are
then submitted to the jurisdictional authority having control
(either the MWRA or the DEP) with the proper permitting documents
and supporting engineering design data for final approval prior
to discharging wastes to the sewer system.
RETURN
TO INFRASTRUCTURE REPORT
TABLE OF CONTENTS
|
