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Operations Report | Infrastructure Report
For more information,
contact David Eppstein by email at
deppstein@masco.harvard.edu,
or by calling 617-632-2860.
2.0 SPECIAL WASTE PIPING AND PRETREATMENT SYSTEMS
In Massachusetts, "Special Waste" includes, but is not
limited to, organisms containing recombinant DNA molecules, chemicals,
nuclear, radioactive, acids, alkalis, perchloric solvents and
other such wastes that could be considered detrimental to the
public sewer system and which do not comply with limitations established
by the Publicly Owned Treatment Works such as the MWRA.
The design, methods, materials, type of neutralization, testing,
and inspections required for "Special Waste" piping
systems serving laboratories and industrial activities are governed
under 248 CMR 2.13 of the Massachusetts State Plumbing Code (12/1/93).
The code establishes the guidelines for the proper installation
methods and materials selection for "Special Waste"
piping systems but not for the way it may be used after
it is installed or what "chemicals" may be disposed
into it on a daily basis.
Constant changes in chemical technology, the rearranging of existing
laboratory spaces, and the lack of versatility in piping systems
have created concerns relative to the safety and operations of
"Special Waste" piping systems. Most recently, the
greatest concern centers on the impact created by historical discharges
of elevated amounts of mercury into these systems. Although the
reduction of the mercury point source from existing waste streams
will address most, if not all, of the non-compliance concerns,
there is still the ongoing issue of biomass absorption of mercury
within the piping system itself.
In particular, the following design guidelines are meant to focus
on the biomass removal from piping systems. However, it must
be noted that these guidelines should be followed when any type
of "Special Waste" is introduced into a dedicated piping
system designed specifically for the conveyance of special wastes.
The following regulatory guidelines have used 248 CMR 2.13
- Piping and Treatment of Special Wastes (12/1/93), as the
primary basis for the design protocol considerations:
248 CMR 2.13 (12/1/93) governs "Special Waste" systems
other than from standard plumbing fixtures.
All plans and specifications for "Special Waste" piping
and pretreatment systems shall be prepared by a Registered Professional
Engineer for submission to the local Plumbing Inspector, MWRA,
DEP or other authorities for their review and approval. Permits
are applied for on the basis of the design and the inspections
of the installed "Special Waste" piping and pretreatment
systems must be made by the engineer during construction.
All "Special Wastes" must be conveyed in a separate
waste and vent piping system. These systems are to be constructed
of approved code materials. A list of these materials and installation
requirements are located in 248 CMR 2.13 (12/1/93).
The Owner shall provide a notarized letter stating what materials
are to be disposed of into the piping system.
All designs must conform with the intent of the regulations.
Alternate design of a system, materials and/or "Special Waste"
termination point shall be considered ONLY where evidence
is presented that certain standards cannot be reasonably complied
with. The plan for such a proposed alternate system shall specifically
be submitted to the local Plumbing Inspector for review and approval.
Piping materials and equipment such as pumps, pits, etc., shall
be constructed of materials chemically resistant and thermally
compatible with the liquids being disposed or pumped.
Great care must be taken in the selection of system materials
in order to be compliant, technically compatible and safe to use
without the danger of leakage and spills. Non-compatible applications
such as hydrofluoric acid with glass piping, high-temperature
waste streams with thermo-plastic piping and non-pressure rated
pipe and fittings on special waste pump discharge lines must be
addressed. Conversely, "Special Waste" piping systems
cannot be used for the conveyance of sanitary type wastes.
Neutralizing sumps or tanks shall be used for the pretreatment
of wastewaters containing dilute acids and alkalis from laboratory
sinks. These sumps are not allowed to adjust the
pH for wastewater generated by biomedical laboratories. These
sumps similarly cannot be used in facilities discharging significant
quantities of organic materials into the "Special Waste"
System or the biomass which is found will coat the marble chips
rendering the media useless. The different types of neutralizing
materials, and approved materials of construction and sizing are
described in 248 CMR 2.13 (12/1/93).
Adjustment tanks for pH are used to treat all "Special Wastes"
including dilute acids and alkalis. The sizing of the pH adjustment
tank (reactor vessel) shall initially be based upon 248 CMR 2.13,
Table 1 (12/1/93), in order to determine hourly flows and relative
retention times. However, diversity factors for estimated flows,
type of wastes (acid and caustic), waste stream temperature, high
flow surges from pumped discharges or equipment dump cycles, future
capacity, etc., all have a bearing on correctly sizing an automatic
pH adjustment system. The anticipated flows through the waste
piping system may dictate the use of a two tank system; the first
tank being a mix tank for rough neutralizing and a trim tank for
final adjustment prior to discharge to the sewer system. 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 and shall be submitted to the local Plumbing Inspector
for approval. Figures 2.1 and 2.2 display typical "Special
Waste" pH adjustment system, and special waste battery system
and vent piping.
Each reactor vessel is to be fitted with an agitator capable of
operating at all times when waste flows occur, a pH monitoring
system for operation of acid/alkali neutralizing media to maintain
a tank pH level of between 5.5 and 10.5, as required by the MWRA's
Sewer Use Rules and Regulation 360 CMR 10.023 (7/2/93) and related
controls. Prior to using any neutralizing media it should be
analyzed for mercury content. Several institutions found that
lower grade neutralizing media contained high concentrations of
mercury. This finding forced the institutions to use a higher
quality reagent grade chemical.
The discharge piping from the reactor vessels shall be fitted
with a trap, pH monitor and recording device, a sampling port
for Regulatory Agency testing, and a flow meter and recording
device, as required.
The MWRA requires that all facilities with industrial wastewater
discharges of 25,000 gallons per day or greater, or subject to
EPA categorical limits with wastewater discharges of 1,000 gallons
per day or greater, monitor flow during compliance sampling.
The recent installation of flow monitoring devices in several
institutions has documented that these institutions had been significantly
over estimating their flow rates. Since the MWRA bases permitting
and sampling fees on flow, an institution may be doing unnecessary
sampling and reporting if flow estimates are not accurate. The
additional sampling and permitting fees may be avoided if actual
flow rates are obtained via flow monitoring devices. In most
cases these devices can pay for themselves from the reduced MWRA
sampling and reporting fees alone.
Systems adjusting pH are to be accessible for maintenance, repair,
operation, and
sampling procedures.
Figure 2.1 pH Adjustment System
Source: Commonwealth of Massachusetts Fuel Gas
and Plumbing Codes,
248 CMR 1.00 - 7.00, pg. 84
Figure 2.2 Special Waste Battery System and Vent Piping
Source: Commonwealth of Massachusetts Fuel Gas
and Plumbing Codes,
248 CMR 1.00 - 7.00, pg. 140
The operation and maintenance requirements
of these pH adjustment systems are detailed in 314 CMR 12.00,
Division of Water Pollution Control regulations. In addition,
these wastewater pretreatment systems are required
to be operated by certified wastewater pretreatment operators.
Certification requirements for wastewater pretreatment operators
are detailed in 257 CMR 2.00, Board of Certification of Wastewater
Treatment Facilities regulations.
The MWRA prefers that institutions use open channel type flow
devices whenever possible and that these devices be compatible
with their samplers for flow monitoring connections. The recommended
open channel flow device for high flow conditions is the Parshall
flume and, for low flow conditions, the Palmer-Bowlus flume is
preferred.
It is not always possible to install open channel flow devices
because of space limitations. In this situation, the use of an
in-line velocity meter to monitor flow is acceptable.
Whichever device is selected, it is very important that these
devices be compatible with the MWRA's sampling equipment. The
MWRA's samplers are capable of receiving direct and indirect signals
from flow monitoring devices. The specific signal requirements
are presented in communication from the MWRA to Beth Israel which
is located in Appendix E.
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