CE U P D A T E POLLUTION PREVENTION
II
David Ornelas, PE
Robert H. Hogrefe, MS, PE
Richard W. Dapson, PhD
Janet Crookham Dapson, MLT(ASCP)
The Role of Recycling and
Chemical Substitution in
Pollution Prevention Programs
ABSTRACT The disposal of certain laboratory chemicals substances to the wastewater treatment plant
(publicly owned treatment works).
provides a challenge from a pollution-prevention
Formaldehyde and various solvents can be
perspective. Using substitutes, treating the chemical, and recycled, although different technologies are used
recycling can solve this problem. Recycling chemicals not for different materials. Simple distillation is useful in separating volatile liquids from solids, and
only provides a pollution-prevention solution for the
as such is ideally suited for formalin recycling.
laboratory, but also cuts down on costs of materials and
Waste formalin may contain buffer or zinc salts as
associated waste disposal. In this article, specific
well as tissue extracts and fragments, in addition
information concerning these waste-management practices to water and formaldehyde. After distillation,
is given for various toxic and hazardous reagents. Together,only water and formaldehyde are reclaimed; thus
these chemicals make up the bulk of hazardous waste
any buffer or zinc salts must be added back to the
solution. Furthermore, the formaldehyde content
generated by medical laboratories.
This is the last article in a two-part series on pollution prevention in the laboratory.
The first article discussed removal of heavy metal waste from the laboratory. On
completion of this series, the reader will be equipped with the tools to execute a
viable and cost-reducing pollution-prevention program and will be able to identify
wastewater pollutants and waste-reduction opportunities for chromium, mercury,
formaldehyde, clearants, alcohols, stains, chromogens, and picric acid.
From the
Wastewater Utility
Division, Public
Works Department,
Albuquerque, NM
(Ornelas and
Hogrefe); and
Anatech, Battle
Creek, Mich (Dapson
and Dapson).
Reprint requests to
David Ornelas,
Wastewater
Utility Division
Headquarters,
4201 2nd St SW,
Albuquerque, NM
87105; or e-mail:
[email protected]
356
As discussed in the first article of this series,
wastewater officials in Albuquerque, NM, worked
with medical laboratories to develop a Biomedical Laboratory Code of Practice to provide the
foundation for a proactive approach to waste
management. An important component of that
program is the handling of hazardous chemicals
commonly found in biomedical laboratories. In
this article, we discuss recycling as a viable option
in a laboratory's pollution-prevention program.
Recycling
Perhaps the most convincing argument for implementing a pollution prevention program in the
laboratory is the cost savings. Nowhere is this more
evident than in the area of recycling. Recycling of
high-volume liquid chemicals reduces expenses by
reducing raw material purchases, waste disposal
fees, and freight charges. Recycling often has other
intangible benefits, such as compliance with waste
disposal regulations and a load reduction of toxic
LABORATORY MEDICINE
VOLUME 29, NUMBER 6
JUNE 1998
must be assayed and adjusted accordingly, which
can be done quickly and easily with salt and assay
kits, including those offered by B/R Instrument
(Easton, Md), CBG Biotech (Columbus, Ohio),
and Anatech (Battle Creek, Mich).
Solvents pose a different problem for recycling
because they often are contaminated with volatile
material (eg, water and alcohol in clearants). Simple distillation (boiling and recovering all volatile
components) rarely is adequate for recycling
them to a satisfactory purity. A more elaborate
technology—fractional distillation—is required
to separate desirable from undesirable volatile
components.1,2
The large capital outlay for a distillation unit
requires careful economic study and justification.
A worksheet used to determine the feasibility of
purchasing a still is presented in Fig 1. Information specific to a particular piece of equipment
(eg, operational cost) can be obtained from vendors. Note that disposal costs may include consulting, assay, pickup, and mileage fees.
Most distillation units use water to cool the
condenser. If large-volume water usage is an environmental or economic concern, recirculation
equipment is an easy remedy.
Xylene, alcohols, and formaldehyde are flammable and toxic, and recycling of these materials
Name of
requires careful consideration. Consult your fire
department, building inspector, and insurance
company to be sure that all hazards are addressed.
Secondary containment is necessary to prevent
spills from spreading and entering the sewer. Solvent waiting to be recycled and solvent still bottoms (the residue left after recycling) should be
managed according to hazardous wastes regulations. The use of on-site recycling reduces waste
volume and can lower your laboratory's hazardous waste generator classification.
Detailed information on recycling specific solvents appears in the next section. With any distillation process, it is critically important to keep
the unit clean. Tissue extracts will burn onto the
heated chamber, releasing volatile amines and
fatty degradation products into the recovered solvent. These will produce unpleasant odors that
will ruin the relatively odorless xylene substitutes
and may even be noticeable in recycled formalin.
Specific Recommendations for Waste
Management
Different materials require different treatment.
Below are recommendations for common laboratory wastes.
Formaldehyde
The hazards associated with workplace exposure to
formaldehyde and formalin solutions are
addressed by the Occupational Safety and Health
Administration's formaldehyde standard.3 Much
less defined is the fate and effect of formaldehyde
on wastewater treatment plants. No uniform standard exists, and some wastewater treatment
authorities allow formaldehyde disposal while others prohibit sewer disposal altogether. In fact,
formaldehyde is readily biodegradable in a publicly
owned treatment works if the concentration does
not inhibit the microbes. Anaerobic sludge digestion is inhibited at 100 ppm, while aerobic digestion is affected at 135 to 175 ppm.4 Microbes
acclimated to the chemical fare better than those
that have had little exposure. If drain disposal of
formalin is allowed, it is better to introduce it
slowly over a period of time rather than dumping
large quantities on an infrequent basis.
Methods of reducing formaldehyde waste
include using substitutes, recycling, and treatment.5 Formaldehyde substitutes are commercially available from several companies. A careful
review of the substitutes' effectiveness, disposal
requirements, and chemical safety is necessary
when considering substitutes.
A. Quantity of recyclable solvent used
gal/y
Costs of Not Recycling
B. New solvent purchase costs
$/gal
C. Freight charges for new solvents
$/gal
D. Total cost of purchasing new solvent:
D = B+C
$/gal
E. Solvent disposal cost
$/gal
F. Total cost of not recycling:
F= D+E
$/gal
G. Total cost of not recycling per year:
G = Fx A
$/y
Recycling—Operation and Maintenance Costs
H. Still operation —labor for 1 year
$/y
I. Still maintenance—labor for 1 year
$/y
J. Power costs for 1 year:
J = A x ($/gal)
$/y
K. Water costs in 1 year
$/y
L. Total operation and maintenance costs for 1 year:
L=H+I+J+K
$/y
Solvent Reconstitution Costs
M. Cost of chemicals to reconstitute solvent after
recycling (if needed, ie, to recycle formaldehyde)
$/y
Still Bottom Costs
N. Still recovery rate
%
0. Still bottom volume:
0 = A x [(100 -
gal/y
N)H-100]
R Cost of disposing of still bottoms:
P= O x E
$/y
Q. Cost of makeup solvent:
Q = Ox D
$/y
R. Total cost of still bottom:
R= P+ Q
$/y
S. Total cost of recycling:
S = L+ M +R
$/y
T. Savings difference with recycling:
T= G - S
$/y
Distillation Unit Costs
U. Capital cost of still
$
V. Still installation —materials
$
W.Still installation-labor
$
X. Total capital cost of still:
X = U + V + W
$
Y. Payback period for recycling:
Y = X-T
y
Fig 1. Worksheet for analyzing the cost of recycling a solvent by on-site distillation.
JUNE 1998
VOLUME 29, NUMBER 6
LABORATORY MEDICINE
1. Terpenes
2. Aliphatic hydrocarbons
3. Other mixtures
Fig 2. This distillation unit is used to recycle xylene
and alcohol from the histology and cytology
laboratories (S. E. D. Medical Laboratories,
Albuquerque, NM).
If substitution is not feasible, waste formaldehyde may be recycled using commercially available
distillation units. Zinc formalin and buffered formalin can be recycled. It is generally not practical to
recycle alcoholic formalin due to the difficulty in
assaying and adjusting the alcohol and formaldehyde content simultaneously.
A third option is to treat formaldehyde and pour
it down the sewer drain. Commercially available
products for treating formaldehyde fall into one of
three categories of chemical treatment:
1. Chemical destruction, during which the
formaldehyde is destroyed
2. Polymerization reactions, during which the
formaldehyde molecule is chemically bonded
3. Fixation or physical adsorption, during which
formaldehyde is loosely attached to other molecules or adsorbed onto resin granules6
Test T i m e !
Look for the CE
Update exam on
Pollution Prevention
(804) in this issue of
Laboratory Medicine.
Participants will earn
2 CMLE credit hours.
Obtain material safety data sheets for the reaction products (ie, subsequent to treatment) and
share these with local publicly owned treatment
works officials. Products that produce solids and
gels should not be poured down the drain because
they can clog sewer lines.
Xylene and Other Clearants
Xylene is mostly flammable, toxic, insoluble in
water, and should not be poured down the drain.
Two pollution prevention opportunities for reducing xylene waste are replacement and recycling.
Xylene substitutes can be divided into three groups:
LAB6RATORY MEDICINE
VOLUME 29, NUMBER 6
JUNE 1998
Of the alternatives, the aliphatics are the safest;
terpenes are sensitizers capable of causing allergic
reactions. Proprietary solvents of undisclosed composition should be avoided for safety reasons as
well as for disposal considerations.
Xylene substitutes do not work exactly like
xylene, so adjustments in processing and staining
protocols usually are necessary. These adjustments
are not difficult, however, and should not stand in
the way of removing a seriously toxic chemical
from the laboratory environment.
No xylene substitute should be poured down
the drain, regardless of the manufacturers' claims.
Biodegradation rates are extremely low, so these
solvents will either end up in the anaerobic digestion tanks of the publicly owned treatment works
or pass through the publicly owned treatment
works to the environment. Either way is highly
undesirable, and discharge to the environment is
illegal. The advantage of xylene substitutes, particularly of the aliphatic hydrocarbon family, is to
provide a healthier workplace. None allow for
easier disposal.
One of the best pollution prevention practices
available is to use on-site fractional distillation to
recycle clearants and solvents (see Fig 2). Xylene
and short-chain aliphatic substitutes can be recycled, ensuring a steady and inexpensive supply.
Long-chain aliphatics (those with flash points
greater than 140°F) should not be distilled
because of their high boiling points. Most terpene-containing clearants have additives that will
not be recovered in the distillation process; any
terpene may undergo auto-oxidation when
boiled, leading to increased viscosity.
Alcohols
Alcohols and alcohol mixtures containing ethanol,
isopropanol, or methanol that are used in fixation,
staining, and slide preparation also may be recycled
in fractional distillation units. The alcohol solutions recommended for recycling include alcohol
from processing and from the last part of the staining setup. Alcohols containing xylene are not suitable for recycling because such mixtures cannot be
separated when alcohol is the intended product of
recovery; these wastes come from the purge cycle
and from the first part of the staining setup. All
recycled alcohol will contain water because alcohols
form an azeotrope with water. The highest quality
alcohol achievable for ethanol and isopropanol are
95% and 88%, respectively.7
Dyes, Stains, and Chromogens
When considering disposal options for stains, look
at the characteristics of the dye and the solvent. Solvents alone may be considered hazardous due to
ignitability and toxicity (eg, ethanol, methanol).
Drain disposal of stains may be undesirable
because of the intense color. Decolorize a stain,
whenever it is possible to do so safely. Household
bleach may be added to eosin solutions (under a
fume hood); do not try this with hematoxylin,
however, because a very irritating and toxic gas
(hydrochloric acid) is given off. Decolorize hematoxylin by adding sodium iodate until the solution
becomes brown.
Chromogens, most commonly including
diaminobenzidine (DAB) and aminoethylcarbazole (AEC), are used extensively in immunohistochemistry. Contrary to popular notion, neither
one can be safely detoxified by mixing with bleach.
DAB is the chromogen of choice because it can be
rendered harmless by oxidizing it with potassium
permanganate 8-10
Picric Acid
Picric acid is used in some fixatives and stains. It
may be explosive when dry, shocked, or heated or
when it comes into contact with metal or metallic
salts. It is toxic by skin contact and should be
avoided as much as possible. If picric acid is dry, call
for a professional hazardous materials team to
remove it. Picric acid leached from specimens into
a processor may cause an explosion if metal
picrates are formed.
Picric acid is no longer needed in the histology
laboratory, and is little used elsewhere. Certain formalin substitutes and zinc formalin solutions will
produce equivalent results when chosen carefully
and used as directed by the manufacturer. As a
bright yellow counterstain, picric acid can be substituted with 0.1% to 0.5% tartrazine (colour
index no. 19140, the Society of Dyers and
Colourists, Great Britain) in water with pH
between 3.0 and 3.5. n
Conclusion
Employees most familiar with the processes are the
best source of ideas for pollution prevention. By
working with regulators, consultants, suppliers, and
in-house personnel, biomedical personnel can
develop the best pollution prevention strategies for
their laboratory.
Pollution prevention improves workplace
safety, reduces wastes and expenses, and protects
the environment. A voluntary, proactive approach
by laboratory personnel will advance these goals.
Material substitutions
and recycling offer the
best opportunities for
pollution prevention.
The most serious hazardous chemical wastes
generated in biomedical
laboratories (formalin,
xylene, mercury, chromium, and picric acid)
can be replaced with
effective
substitutes,
sometimes at a much
lower overall cost. Recycling will greatly reduce
the amount of hazardous waste for the
three highest-volume
chemicals (formalin,
alcohol, and xylene).©
Please let us know your opinion of the
Pollution Prevention (804) series.
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abstract.
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Comments: (Attach additional pages, if
necessary.)
Acknowledgments
The authors would like to
acknowledge Daniel Gates
Thank you for your input. Mail this form (or
and Brynda Gutierrez of the
a photocopy) alone or with your exam to:
Pollution Prevention ProLaboratory Medicine, 2100 W Harrison St,
gram, Wastewater Utility
Chicago, IL 60612-3798.
Division, Public Works
Department, City of Albuquerque, and numerous persons in laboratories contacted in
Albuquerque for their contributions to the Biomedical Laboratory Code of Practice.
References
1. Dapson JC, Dapson RW Hazardous Materials in the
Histopathology Laboratory: Regulations, Risks, Handling and Disposal. Battle Creek, Mich: Anatech; 1995:139-145.
2. Reinhardt PA, Leonard LK, Ashbrook, PC. Pollution Prevention and Waste Minimization in Laboratories. Boca Raton, Fla:
CRC Press; 1996:240-243.
3. 29 CFR §1910.1048.
4. Verschueren K. Handbook of Environmental Data on Organic
Chemicals. New York, NY: Van Nostrand Reinhold;
1983:678-683.
5. Strine E, Marty JJ, Bentley JD. Improving biopsies diagnostic cycle-time while preserving optimal cellular morphology.
Shandon Lipshaw LabLeader. 1996;11:8-9.
6. Dapson JC, Dapson RW. Hazardous Materials in the
Histopathology Laboratory: Regulations, Risks, Handling and Disposal. Battle Creek, Mich: Anatech; 1995:165.
7. Dapson JC, Dapson RW. Hazardous Materials in the
Histopathology Laboratory: Regulations, Risks, Handling and Disposal. Battle Creek, Mich: Anatech; 1995:143.
8. Dapson JC, Dapson RW. Hazardous Materials in the
Histopathology Laboratory: Regulations, Risks, Handling and Disposal Batde Creek, Mich: Anatech; 1995;162-163.
9. Lunn G, Sansone EB. Destruction of Hazardous Chemicals in
the Laboratory. New York, NY: J Wiley 8( Sons; 1990:35-41.
10. Lunn G, Sansone EB. The safe disposal of diaminobenzidine. Appl Occup Environ Hyg. 1991;6:49-53.
11. Dapson JC, Dapson RW. Hazardous Materials in the
Histopathology Laboratory: Regulations, Risks, Handling and Disposal. Battle Creek, Mich: Anatech; 1995:132.
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