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Tech. Identification
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For more
information, contact David Eppstein by email at
deppstein@masco.harvard.edu,
or by calling 617-632-2860.
II. TYPES OF HOSPITAL WASTEWATER
Wastewater
produced by hospitals and by hospital-related industries
originates from many sources. The Technology Identification
Subgroup assigned the various medical industry wastewater
streams into the following four categories:
- wastewater from
Clinical Laboratories.
- wastewater from
Research Laboratories.
- wastewater from
Medical Waste Incinerators equipped with fume scrubbers.
- wastewater from
Hospital Laundries.
To
understand the characteristics of these wastestreams and the
difficulties that might be encountered when attempting their
pretreatment, it is important to understand the operations or
sources of waste that contribute pollutants to the individual
wastestreams. In this way, the chemical constituency of each
wastestream can be predicted and potential interferences in a
mercury removal process can be anticipated.
The
following are brief overviews of typical wastewater-producing
processes in each category of hospital facility. Each overview
includes an interpretation of the analytical data generated from
a wastewater sampling and analyses project that was performed at
a representative facility. The wastewater sampling and analysis
project was performed by a subgroup of the Phase II Work Group
known as the Wastewater Characterization (WWC) Subgroup. Refer
to the next section of this report for a summary of the WWC
Subgroup project.
Clinical
Laboratories:
Most
clinical laboratories perform a wide range of services but not
every clinical laboratory is the same. Some clinical
laboratories are independent of hospitals. Generally, the larger
the hospital, the greater the extent of services offered by the
clinical laboratory.
The
types of processes performed in a clinical laboratory can
include: anatomic pathology (including routine histology and
cytology), chemistry, drug monitoring and toxicology,
hematology, immunology and serology, microbiology, transfusion
medicine, and urinalysis. In addition, there can be cytogenetics,
flow cytometry, histocompatibility testing, molecular pathology,
mycology, and nuclear medicine.
Wastewater
from a "typical" clinical laboratory could contain
ionic mercury and organomercuric compounds, other heavy metals,
organic chemicals, blood products and body fluids, formaldehyde,
buffers, dilute mineral acids/bases, phosphates, oxidizers, oil
& grease, and particulate materials. Data from the Work
Group’s Wastewater Characterization Study suggests that
clinical laboratory wastewater would have higher biochemical
demand (BOD) and chemical oxygen demand (COD) than domestic
sewage. Because there is usually some standardization of work,
the wastewater from a specific clinical laboratory may be
somewhat consistent in quality and characteristics over long
periods.
Research
Laboratories:
Perhaps
the most diverse and unpredictable wastestreams are those
discharged from research laboratories. Many medical institutions
are conducting "cutting edge" studies in infectious
disease control, blood chemistry, pathology, animal research and
inorganic chemistry. Wastes may be produced in significant
quantities for short periods or not at all for extended periods.
Research laboratory facilities in hospitals can range from one
to two laboratory sinks that produce "tens of gallons"
each day to hundreds of sinks and related fixtures generating
waste volumes in excess of fifty thousand gallons per day.
Wastes
can originate from either automated instrumentation or from
manual processes and may contain the following pollutants:
oxidizers (disinfecting media such as bleach, iodine, peroxides,
etc.), radionuclides, proteins (tissue and immunodiagnostics),
oil & grease (from vacuum pumps and other rotating
equipment), heavy metals (analytical reagents), organic
solvents, blood products and other body fluids (urea is a
well-known chelator of heavy metals), formaldehyde, phosphates
and detergents (from glass cleaning and instrument sterilizing
processes), and photographic imaging chemicals (desilvered spent
fixer and developer solutions). Data from the Work Group’s
Wastewater Characterization Study suggests that (BOD) and (COD)
are lower than for clinical laboratories but above average
compared with domestic sewage.
Medical
Waste Incinerators:
Federal
and State regulations closely govern the management of
infectious medical or "Red Bag" wastes. Some
facilities, trying to reduce the cost of offsite waste disposal,
have chosen to install on-site medical waste incinerators to
burn these wastes. Air quality regulations typically require the
installation of emission controls on the incinerator stacks for
particulate and oxides of nitrogen (NOx) and sulfur (SOx).
Most control systems involve a fume scrubber where pollutants
are scrubbed from the waste gas stream into a recirculating
water stream. To limit the concentration of pollutants in the
recirculating water, part of the water is typically discharged
into a sewer system and is replaced with fresh water.
Mercury
in the waste gas stream can originate from the waste being
burned and also from the fuel used to burn the waste. Red Bag
wastes may contain tissue, paper, saturated sorbents, plastics,
mercury thermometers, and metallic objects. In some facilities,
various animal or human tissues may be disposed of as Red Bag
wastes. The liquid wastestream from the incinerator scrubber
usually has relatively low concentrations of organic material,
oxidizers, but can contain significant concentrations of
particulate matter and heavy metals (including mercury). BOD and
COD concentrations for incinerator wastewater are usually lower
than those of domestic sewage.
Hospital
Laundries:
Hospital
laundries typically process linens, gowns and lab coats that
will contribute a certain amount of organic material, fats, oils
and grease (FOG) and an alternating range of pH (alkaline
detergent followed by an acidic sanitizer) to the wastestream.
This is notably different from a commercial laundry that will
commonly process garments, uniforms, wipers, mops and mats often
contaminated with heavy metals and petroleum products. Depending
upon the processes employed, the hospital laundry wastestream
can have elevated temperatures and pH extremes and can contain
starch, particulate (including lint), proteins (blood products),
detergents, and oxidizers (bleach or other disinfectant). BOD
and COD concentrations from laundry wastewater are usually in
the normal range for domestic sewage.
Some
laundry chemicals (sodium hydroxide and bleach) are known to
often have significant levels of mercury contamination. In
addition, just one broken mercury thermometer can cause
temporary high levels of mercury in the laundry wastewater.
Hospital laundry wastewater flows can vary from a few hundred
gallons per day to many thousands of gallons per day.
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