Laboratory and Medical Equipment
7.1 Water Purification
WaterSense
at Work
Best Management Practices for
Commercial and Institutional Facilities
EPA
WaterSense
March 2024
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WaterSenseฎ is a voluntary partnership program sponsored by the U.S. Environmental
Protection Agency (EPA) that seeks to protect the nation's water supply by transforming
the market for water-efficient products, services, and practices.
WaterSense at Work \s a compilation of water efficiency best management practices
intended to help commercial and institutional facility owners and managers from multiple
sectors understand and better manage their water use. It provides guidance to help
establish an effective facility water management program and identify projects and
practices that can reduce facility water use.
An overview of the sections in WaterSense at Work is below. This document, covering
water efficiency for water purification systems, is part of Section 7: Laboratory and
Medical Equipment. The complete list of best management practices is available at
www.epa.gov/watersense/best-management-practices. WaterSense has also developed
worksheets to assist with water management planningand case studies that highlight
successful water efficiency efforts of building owners and facility managers throughout the
country, available at www.epa.gov/watersense/commercial-buildings.
Section 1. Getting Started With Water Management
Section 2. Water Use Monitoring
Section 3. Sanitary Fixtures and Equipment
Section 4. Commercial Kitchen Equipment
Section 5. Outdoor Water Use
Section 6. Mechanical Systems
Section 7. Laboratory and Medical Equipment
Section 8. Onsite Alternative Water Sources
EPA 832-F-23-003
Office of Water
U.S. Environmental Protection Agency
March 2024
This document is one section from WaterSense at Work: Best Management Practices for Commercial and
Institutional Facilities (EPA-832-F-23-003). Other sections can be downloaded from
vwwv.epa.gov/watersense/best-management-practices. Sections will be reviewed and periodically updated
to reflect new information. The work was supported under contract 68HERC20D0026 with Eastern Research
Group, Inc. (ERG).
March 2024
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Laboratory and Medical Equipment
Water Purification
Overview
Water purification systems are used in laboratory and medical applications requiring high-
quality water that is free of minerals and organic contaminants. Generally, these systems
purify water through physical or chemical processes. Many water purification systems use
additional water during a backwash phase to remove particle buildup on the purification
media or discharge a reject stream containing concentrated contaminants.
The various water purity levels (i.e.,
types or grades) required depend on the
specific applications or end uses at the
facility. There are several technical
standards for water quality that
facilities can use to help determine the
appropriate water purity level needed
for an application, including the ASTM
International D1193 Standard
Specification for Reagent Water and the
International Organization for
Standardization (ISO) 3696 Water for
Analytical Laboratory Use
Specification and Test Methods. Once
researchers determine the water purity
level needed, lab managers can choose one or more water purification technologies that
will achieve that water quality grade.
There are a number of water purification technologies that can be considered. These
include: sediment and microporous filtration; carbon filtration; reverse osmosis and other
membrane processes; water softening; deionization; and distillation. Because no single
water purification system is able to remove 100 percent of all contaminants, it is common
for multiple water purification technologies to be installed in sequence where only a low
level of impurities or contaminants can be tolerated. Typically, as finer particles are
removed, the purification process becomes more water- and energy-intensive and
potentially more expensive to operate. Therefore, it is important to evaluate the level of
water quality required to ensure that the system does not deliver a higher level of
purification than is needed. Further, facility managers should work with researchers to
evaluate what grade of water is needed to support the majority of their operations, and
design centralized treatment systems to supply that grade. If higher-purity water is needed
WaterSense
Water purification system in a laboratory
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for certain applications, polishers or point-of-use treatment equipment can be used as
necessary.1
Sediment and Microporous Filtration
Sediment and microporous filtration (e.g., microfiltration, ultrafiltration) physically remove
suspended solid contaminants greaterthan the filter's rated pore size by capturingthem
on the surface of the media. Microporous filtration typically occurs at low pressures and
does not remove any dissolved solids. As shown in Figure 1, microfiltration can remove
particles down to 0.1 micron in size, and ultrafiltration can remove particles down to 0.01
micron.2 After a period of use, filters will require backwashing with water to remove
contaminants trapped on the media surface. To reduce water use from filtration
processes, facilities can use pressure sensors to determine when the pressure drop in the
filter is significant enough to require backwashing and conduct backwashing as
infrequently as possible.3 Some filtration processes include single-use cartridge filters that
don't require backwashing, but they have to be disposed of when the filter is changed.
Figure 1. Water Contaminants Removed by Different Levels of Filtration and
Membrane Processes
Microfiltration Ultrafiltration Nanofiltration Reverse Osmosis
>0.1 micron 0.1-0.01 micron 0.01-0.001 micron <0.001 micron
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Carbon Filtration
Carbon filtration uses adsorption to remove chlorine and dissolved organics as water
passes through the filter. Carbon filters can use either disposable cartridges or packed
1 National Institutes of Health (NIH). March 2013. Laboratory Water, Its Importance and Application. Page 13.
https://orf.od.nih.gov/TechnicalResources/Documents/DTR%20White%20Papers/l_aboratorv%20Water-
lts%20lmportance%20and%20Application-March-2013 508.pdf.
2 International Institute for Sustainable Laboratories (I2SL) and U.S. Environmental Protection Agency (EPA).
May 2022. Best Practices Guide: Water Efficiency in Laboratories. Page 8.
www.epa.gov/svstem/files/documents/2022-06/ws-l2SL-Laboratorv-Water-Efficiencv-Guide.pdf.
3 Ibid.
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columns. Disposable cartridges are disposed of once the adsorptive capacity is
exhausted. Alternatively, packed columns can be removed and regenerated off-site. Water
use is required to regenerate the columns; however, when regeneration occurs off-site
(which istypical), this would not impact facility water use. Although facility water use won't
be impacted by off-site regeneration, facilities are still encouraged to regenerate packed
columns only when necessary.
Reverse Osmosis and Other Membrane Processes
Membrane processes use a semi-permeable membrane layerto remove impurities at a
smaller level than microporous filtration. As illustrated in Figure 1 on page 2, nanofiltration
can remove particles down to 0.001 micron in size, and reverse osmosis can remove
particles even less than 0.0001 micron.4 Reverse osmosis membranes are able to reject
bacteria, pyrogens, and organic and inorganic solids. Because reverse osmosis is capable
of removing the smallest particles, it is used most often by laboratory and medical
facilities requiring very pure water, and it is the most water-intensive membrane process.
Reverse osmosis units use pressure to
reverse osmotic pressure and force
water with a high solute concentration
through a membrane filter to create
purified (i.e., low solute) water. Reverse
osmosis removes a large portion of
contaminants but recovers only a
portion of the incoming water. Reverse
osmosis systems produce two streams
of water: the purified water (i.e.,
permeate) and the concentrated reject
water, which contains a high level of
dissolved minerals and is typically sent
to the sanitary sewer. The percent
recovery (also known as the recovery
rating), defined as the ratio of permeate to feed (i.e., incoming) water, is used to depict the
efficiency of a reverse osmosis system. For commercial and institutional applications,
reverse osmosis units typically have recoveries of 50 to 75 percent.5,6 Thus, the systems
reject 25 to 50 percent of water entering the system. Reverse osmosis systems can be
optimized to increase percent recovery and reduce water use by pretreating incomingfeed
waterto remove suspended and dissolved solids using other water purification
technologies; using advanced membrane technologies (e.g., membranes with larger
4 Ibid.
5 Hoffman, H.W. (Bill), et. al. May 2018. Best Management Practices for Commercial and Institutional Water
Users. Prepared for the Texas Water Development Board. Page 44.
www.twdb.texas.gov/conservation/BMPs/CI/index.asp.
612SL and EPA, op. cit., Page 9.
Laboratory reverse osmosis system
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surface area and/or higher permeability); and optimizing system flow configurations to use
multiple stages of membranes or recycling a portion of the concentrated reject water. Fully
optimized systems can achieve recoveries greater than 90 percent.7
Water Softening
Water softening is used to remove hardness minerals, such as calcium and magnesium,
from water. Facilities often use water softeners to generate boiler feed water or pretreat
water before it goes through other water purification technologies. Cation exchange water
softeners are the most common type of water softening system, although other water
purification technologies, such as reverse osmosis and distillation systems, can also
soften water.
In a cation exchange water softener, hard water with positively charged calcium and
magnesium ions passes through a mineral tank consisting of positively charged sodium
ions attached to a bed of negatively charged resin beads. The calcium and magnesium
ions are exchanged for the sodium ions on the resin beads, which causes the gradual
depletion of available ion exchange sites. Eventually, the water softener must be
regenerated to replenish the softening capacity. The regeneration process uses water to
purge and rinse the system and replenish the sodium ion supply on the resin beads. As a
result, the system generates sodium-rich wastewater that must be disposed.
The frequency of regeneration and the amount of water used by the water softening
process is dictated by the hardness of the incoming water, the rate of water consumption,
and the hardness removal capacity of the cation exchange water softener. The most
efficient cation exchange water softeners are demand-initiated, which base the frequency
of regeneration on the incoming water's hardness or the demand for softened water rather
than a set regeneration schedule. Regeneration typically happens onsite and, therefore,
impacts a facility's overall water use.
It is also important to consider how much water is used during regeneration and the water
softener's salt efficiency. Efficient water softeners can use 4 gallons (15 liters) of water or
less per 1,000 grains of hardness removed and can achieve at least 3,500 grains of
hardness per pound of salt.8
7 U.S. Department of Energy (DOE), Federal Energy Management Program (FEMP). August 2013. Reverse
Osmosis Optimization. Pages 4-11. vwwv.energv.gov/femp/articles/reverse-osmosis-optimization.
8 ASHRAE and ICC. 2020. ANSI/ASHRAE/ICC/USGBC/IES Standard 189.1-2020. Standard for the Design of
High-Performance Green Buildings Except Low-Rise Residential Buildings. Page 33.
www.ashrae.org/technical-resources/standards-and-guidelines/read-onlv-versions-of-ashrae-standards.
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Deionization
Deionization is a physical process similar to
water softening that exchanges cations and
anions present in the untreated water with
hydrogen and hydroxide ions. Deionization is
not effective at removing particulates,
bacteria, or viruses, but because the process
is relatively fast, it is commonly used in
laboratory applications requiring a low level of
water purification. Similar to activated carbon
filters, deionization resins must be regenerated
periodically to ensure effectiveness, and
regeneration often occurs off site. Water use is
required to regenerate the resin; however,
when regeneration is done off-site (which is
typical), no water is used at the facility level.
Facilities are still encouraged to send resins for
regeneration only when necessary.
Distillation
Distillation functions by boiling water to form
steam condensate using either an electric or
gas still. Solid contaminants are left behind as the steam is generated, then the steam is
condensed into a purified water stream. Smaller units are often more water-efficient since
they can have no discharge, whereas larger systems typically reject 15 to 25 percent of
water entering the system to prevent scale buildup.9 If once-through cooling water is used
in the condenser, a substantial amount of water can be used duringthe distillation
process. Replacing distillation equipment that uses single-pass cooling with air-cooled
models and using a central chilled or condenser water loop to provide cooling are more
water-efficient options. In general, it is best to avoid simple distillation and use other
methods of water purification, as it can be energy-, time-, labor-, and cost-intensive.10,11
Other Technologies
Several less common technologies are also used to purify water. Chlorine compounds,
ozone, or hydrogen peroxide can be used to chemically disinfect water. Ultraviolet light,
heat, and extreme mechanical sheer can also be used to treat water with contaminants.
9 East Bay Municipal Utility District (EBMUD). 2008. WaterSmart GuidebookA Water-Use Efficiency Plan
Review Guide for New Businesses. Page TREAT4. www.ebrnud.com/water/conservation-and-
rebates/cornmercial/watersmart-guidebook.
10 ASHRAE and ICC, op. cit., Page 31,
11 NIH, op. cit. Page 9.
Deionization resin tanks
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These technologies might not require the backwash phase used by other water-purification
technologies, but they can require regular cleaning, which can be water intensive.
Chemical disinfection can use additional water if chemicals are added in liquid or slurry
form.12
Operation, Maintenance, and User Education
For optimal water purification system efficiency, consider the following operation,
maintenance, and user education techniques:
Use water purification only when necessary and match the process to the actual
quality of water required.
For filtration processes, base backwash phases upon the pressure differential
across the filtration media. A pressure drop will indicate that the filter requires
backwashing.
For reverse osmosis systems, if water meters are installed on the incoming feed
water and permeate water lines, read the meters regularly to ensure the system is
achieving its intended percent recovery rate. In addition, ensure a continuous
commissioning process is in place to ensure the system is functioning optimally.13
For water softeners, work with a plumbing professional orthe product manufacturer
to account for and program regeneration based on the incoming water hardness
and/or flow through the system. Monitor and adjust settings periodically.
For carbon filtration and deionization processes where regeneration occurs off-site,
work with maintenance professionals to determine an optimal schedule for
removing and regenerating units. This can be determined based on incoming water
characteristics and the amount and quality of purified water required daily.
Deionization systems should require regeneration based on the volume of water
treated or conductivity. Facilities are encouraged to regenerate only as needed.
For distillation systems, periodically clean the boiling chamber to remove
accumulated minerals. This will ensure efficient operation of the system.
Retrofit Options
Facilities might choose to install multiple water purification systems in sequence to
increase the effectiveness and efficiency of the water purification process. For example,
when one of the later phases of treatment uses a membrane, at a minimum, it might be
necessary to install a pretreatment step to remove larger particles.
12 EBMUD, op. cit.
13 DOE, FEMP, op. cit. Pages 18-19.
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For filtration processes, consider installing pressure gauges, if not already installed.
Pressure gauges can be used to determine when to initiate a backwash phase.
For carbon filtration, deionization, or water softening processes, consider installingwater
meters and/or conductivity meters so regeneration can be based on the volume of water
treated or conductivity instead of a set schedule.
For reverse osmosis systems, consider installingwater meters on the incoming feed water
and permeate water lines and reading them regularly to ensure the system is achieving its
intended recovery rate. Consider retrofitting reverse osmosis systems to optimize the
configuration by adding pretreatment, multiple stages, or reject water recycling systems.
Consider reusingwater purification system reject water as an alternative onsite water
source where appropriate and feasible. See
WaterSense at Work Section 8: Onsite
Alternative Water Sources at
www.epa.gov/watersense/best-management-
practices for more information.
Replacement Options
Priorto purchasing a new water purification
system or replacing an old one, evaluate the
incoming water supply and assess the quality
and quantity requirements of the intended use
for a period of time. This will help to determine
the level of water purification needed and the
sizing of the system. Choose the least
intensive treatment needed to achieve the
desired quality level and size the system
correctly for the intended use. Oversized
systems can waste water and energy and lead
to degraded quality due to long, inoperable
periods. Consider using point-of-use treatment
systems where highly purified water use is
limited.
Select water purification systems that require the least amount of backwashing or
regeneration or that are designed to optimize water efficiency. For specific systems,
consider the following:
For filtration processes, ensure the system has a pressure gauge to determine when
to initiate a backwash phase.
Example point-of-use treatment unit that provides
purified water at the laboratory work station
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For membrane processes such as reverse osmosis, choose a system with a high
recovery rate for its size and that can achieve a minimum recovery rate of 50
percent.14 Design your system with an optimized configuration that may include
feed water pretreatment, advanced membrane technologies, and multiple stages
and/or concentrated reject water recycling.15 If not recycled within the system,
consider whether the reject water could be used in the facility. See WaterSense at
Work Section 8: Onsite Alternative Water Sources at
www.epa.gov/watersense/best-management-practices for more information.
For water softeners, select demand-initiated systems instead of systems with
manual or auto-initiated regeneration. In addition, consider installing multiple
smaller, more efficient cation exchange water softeners that can be alternated to
minimizethefrequency of regeneration and allowfora constant, uninterrupted
supply of soft water. Look for systems that use 4 gallons (15 liters) of water or less
per 1,000 grains of hardness removed. For salt efficiency, look for systems that can
achieve at least 3,500 grains of hardness per pound of salt.16
For carbon filtration and deionization systems, select systems that regenerate
based on the volume of water treated or conductivity.
Facilities should avoid simple distillation systems for water purification.17 If
distillation systems are necessary, choose units that use air-cooled coils rather
than water-cooled coils and that recover at least 85 percent of the feed water.18
Savings Potential
The water use of a water purification system is dependent upon the level of purification
required, incoming water quality, volume of use, and purified water demand. Water use is
also specific to the type of water purification system used.
For filtration processes, water use is determined by the water quality requirements and
frequency of the backwash phase. Optimizingthe frequency of the backwash phase by
initiating backwash only when a pressure drop occurs across the filter media will ensure
less water is used overall.
The water efficiency of a reverse osmosis process can be determined by the recovery rate,
which is defined as the ratio of permeate to feed water. Systems with higher recovery rates
are considered more efficient because they are able to produce more purified waterfrom
the same amount of feed.
14 Hoffman, H.W. (Bill), et. aL, op. cit.
15 DOE, FEMP, op. cit. Pagesvi-19.
16 ASHRAE and ICC, op. cit. Page 33.
17 ASHRAE and ICC, op. cit. Page 31.
18 Hoffman, H.W. (Bill), et. aL, op. cit. Page 41.
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Recovery rates can vary widely depending upon the type of membrane, quality of incoming
water, system configuration, and system operation. Large reverse osmosis systems
typically have a recovery rate between 50 to 75 percent. When a reverse osmosis system is
optimized, however, recovery rates can exceed 90 percent.19 For example, the Sandia
National Laboratories in Albuquerque, New Mexico, installed a high-efficiency reverse
osmosis system with pretreatment before the membranes. The facility was able to achieve
a 95 percent recovery rate, rejecting only 5 percent of the water enteringthe system.20
For water softeners, water use is dependent on the frequency and efficiency of
regeneration. Demand-initiated water softeners initiate regeneration based on the
incoming water's hardness, the volume of water softened, or treated water conductivity
ratherthan a set schedule. Beyond how regeneration is initiated, water consumption
during regeneration can vary. Systems can use 4 gallons (15 liters) of water or less per
1,000 grains of hardness removed.21
Carbon filtration and deionization systems are typically regenerated off-site. If regenerated
off-site, the water use of these systems will not directly affect the water use of the facility.
However, minimizing the frequency of removal and regeneration will help to reduce the
water use of these systems.
The water use of distillers is dependent upon the method of cooling and the amount of
reject water used to clear the boiler of scale buildup. Water savings can be maximized if
air-cooled coils are used ratherthan water-cooled coils. Additionally, systems that
produce less reject water will consume less water overall.
Additional Resources
ASHRAE and the International Code Council (ICC). 2020. ANSI/ASHRAE/ICC/USGBC/IES
Standard 189.1-2020. Standard for the Design of High-Performance Green Buildings Except
Low-Rise Residential Buildings. Pages 30-33. www.ashrae.org/technical-
resources/standards-and-guidelines/read-only-versions-of-ashrae-standards.
East Bay Municipal Utility District (EBMUD). 2008. WaterSmart GuidebookA Water-Use
Efficiency Plan Review Guide for New Businesses. Pages TREAT1 -6.
www.ebmud.com/water/conservation-and-rebates/commercial/watersmart-guidebook.
Hoffman, H.W. (Bill), et. al. May 2018. Best Management Practices for Commercial and
Institutional Water Users. Prepared for the Texas Water Development Board. Pages 38-44.
www.twdb.texas.gov/conservation/BMPs/CI/index.asp.
19 DOE, FEMP, op. cit. Page 5.
20 DOE, FEM P. August 2009. Microelectronics Plant Water Efficiency Improvements at Sandia National
Laboratories. Page 2. www.nreLgov/docs/fv09osti/46334.pdf.
21 ASHRAE and ICC, op. cit. Page 33.
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International Institute for Sustainable Laboratories (I2SL) and U.S. Environmental
Protection Agency (EPA). May 2022. Best Practices Guide: Water Efficiency in Laboratories.
www.epa.gov/system/files/documents/2022-06/ws-l2SL-l_aboratory-Water-Efficiency-
Guide.pdf.
National Institutes of Health (NIH). March 2013. Laboratory Water, Its Importance and
Application.
https://orf.od.nih.gov/TechnicalResources/Documents/DTR%20White%20Papers/Laborat
ory%20Water-lts%20lmportance%20and%20Application-March-2013 508.pdf.
U.S. Department of Energy (DOE), Federal Energy Management Program (FEMP). August
2013. Reverse Osmosis Optimization, www.energy.gov/femp/articles/reverse-osmosis-
optimization.
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Disclaimer
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and opinions of authors expressed herein do not necessarily state or reflect those of the United
States Government nor any agency thereof.
c,EPA
United States Environmental Protection Agency
(4204M)
EPA 832-F-23-003
March 2024
vwwv.epa.gov/watersense
(866) WTR-SENS (987-7367)
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