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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.
6.0 TRAP CLEANING
As explained in the problem overview, mercury accumulation within
"Special Waste" conveyance piping systems containing
biomass growth creates a complicated wastewater compliance issue.
The following procedures have been developed for use during trap
removal and cleaning maintenance. Trap cleaning and removal procedures,
in section 6.5, will accomplish the following objectives: trap
location / identification, removal of elemental mercury (Hg0)
and removal of biomass growth.
Trap location is accomplished by preparing a complete and detailed
inventory of all "Special Waste" sources. After all
sources are identified, a facility "Special Waste" conveyance
pipe drawing should be generated with all traps to be identified
by a unique number. A master inventory of all traps should be
generated to record and track all trap cleaning events. Each
individual trap should be tagged or labeled with its unique number,
cleaning date, name and signature of the person performing the
cleaning.
Trap identification can be accomplished as a part of locating
the necessary information to generate the conveyance pipe drawings.
An additional piece of information would include the type of
piping material and associated trap. Figure 6.1 contains an example
of a trap inventory spreadsheet.
When a trap is removed for the first time, it may contain elemental
mercury. This can usually be identified as a pool of silvery
liquid which is separated from the trap wastewater. Elemental
mercury usually and accidentally gets disposed down laboratory
sinks and floor drains as a result of broken laboratory equipment.
Some elemental mercury sources include old mercury thermometers,
thermostats and blood pressure manometers. If a trap contains
elemental mercury, it should be collected and disposed as a mercury
waste. Section 10.0 of this manual explains the procedures for
disposal of mercury wastes.
Typically a trap will not contain elemental mercury, but almost
every trap and conveyance pipe will eventually accumulate biomass.
The biomass is identified as a slimy light or dark brown film
on the internal surface of the plumbing material. It has been
determined that the biomass, over several years, will accumulate
dissolved
mercury from various chemical reagents and other laboratory chemicals.
Figure 6.1 Example Trap Inventory Spreadsheet
The bulk of this growth will occur on the bottom and wetted sections
but some biomass will grow along the sides and top of the non-wetted
section of the plumbing materials. This capillary action of growth
is the most difficult to remove. When the biomass grows on the
non-wetted surfaces it eventually dries out. This dried out biomass
develops a strong adhesion to the plumbing surfaces as it becomes
encrusted.
- Identify necessary traps for cleaning and discuss the trap
cleaning operation with the building's occupants. Explain to
them how the effect of the cleaning will interrupt their operations
and indicate for how long.
- Before any traps are removed, it is important to ask the occupants
about the nature of their laboratories' wastes, identifying health
and safety hazards. Before handling and cleaning traps that are
located in areas that contain hazardous materials, all traps should
be checked by the appropriate administrator for approval (i.e.
- if a radioactive isotope is being used in a room, have the Radiation
Safety Department check out the trap to assure that it is safe
for cleaning).
- After the building occupants have been made aware of the trap
cleaning program and it is determined that it is safe to handle
traps, actual trap cleaning can be started.
- It is important that personal protective equipment (PPE) be
worn by all personnel doing this trap cleaning at all times.
It is recommend that all of these procedures be reviewed by an
internal Health and Safety Officer.
- All materials found inside the traps must be handled and disposed
as mercury waste. Section 10.0 of this manual explains the procedures
for the disposal of mercury waste.
- The removed trap can be cleaned with either a rag or flexible
brush. The use of a cleaning agent and some type of disinfectant
may also be used to help ensure that complete removal and disinfection
is accomplished
- After traps are removed, cleaned and replaced, a tag or label
should be put on or updated with the unique number, date of cleaning
and the cleaner's initials.
- After cleaning is completed and the area is returned to its
original condition, all access panels and other structural materials
should be reinstalled. Before leaving the area, inform the building
occupant that the cleaning is complete.
- All trap cleanings should be logged on the Trap Inventory Form.
- It will be necessary, in the future, to inspect these traps
for reoccurring biomass growth. These inspections should initially
be performed on a quarterly basis. Once a sufficient level of
experience has been obtained, inspection frequencies can either
be increased or decreased, depending on the rate of returning
biomass.
- NOTE: Have spare traps available for replacement.
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