7-16
WaterSense at Work: Best Management Practices for Commercial and Institutional Facilities
7.4
Steam Sterilizers
Overview
Disinfection/sterilization is common in hospitals and research
institutions where it is necessary to destroy microorganisms that
can cause infection or disease. A steam sterilizer (a subcategory
of autoclaves) is the most common type of system used to dis-
infect and sterilize laboratory equipment, surgical instruments,
medical waste, and other materials requiring sterilization.
23
Steam sterilizers can use water in three ways: to generate steam
(
i.e., the disinfecting/sterilizing agent); to cool steam condensate
to appropriate temperatures before it is discharged down the
drain; and to draw a vacuum through the sterilization chamber
to expedite the drying process.
Several other types of autoclaves use different modes of sterilization, including dry
heat, ethylene oxide, and radiation.
24
However, these modes of sterilization are not
typically recommended unless the material being sterilized has special requirements
that make it adverse to steam or high temperatures. This section focuses on steam
sterilizers, the type of sterilization equipment that uses water.
The water-efficiency options discussed in this section do not address the water used
to generate the steam that is used in the disinfection process and, therefore, do not
impact the steam sterilizer’s ability to disinfect and sterilize equipment. For informa-
tion on optimizing a central boiler and steam system which may supply steam to
steam sterilizers, refer to
Section 6.5 Boiler and Steam Systems
.
Steam sterilizers are usually operated 24 hours per day
in order for the equipment to remain sterile and ready
to use at any time. Most systems are only actively steril-
izing for eight hours per day or less and are idle for the
remaining time.
25
During idle mode, low-pressure steam
is passed into the chamber. During both idle mode
and active sterilization, as the steam in the chamber
condenses, the generated condensate discharges to a
floor drain, where it is tempered with cool water to a
temperature less than 140°F before it is discharged to
the sanitary sewer. Most steam sterilizers use temper-
ing water at a flow rate of 1.0 to 3.0 gallons per minute
(
gpm).
26
Older steam sterilizers can waste a significant amount of water if they allow
tempering water to flow continuously.
27
Even at a flow rate of 1.0 gpm, the resulting
tempering water use can range from 400,000 to 500,000 gallons per year.
Steam sterilizer exterior
Steam sterilizer interior
23
Alliance for Water Efficiency (AWE). Steam Sterilizer & Autoclaves Introduction.
24
Ibid
.
25
U.S. Environmental Protection Agency (EPA) and U.S. Energy Department (DOE), Energy Efficiency & Renewable Energy (EERE), Federal Energy Management Pro-
gram (FEMP). May 2005.
Laboratories for the 21
st
Century: Best Practices, Water Efficiency Guide for Laboratories
.
Pages 5-6.
26
Ibid
.
27
AWE,
op. cit
.
