7-4
WaterSense at Work: Best Management Practices for Commercial and Institutional Facilities
7.2
Water Purification
Overview
Water purification systems are used in laboratory and medical applications requir-
ing high-quality water that is free of minerals and organic contaminants. Generally,
these systems purify water through physical or chemical means. Many water puri-
fication systems use additional water during a backwash phase to remove particle
buildup on the purification media, or discharge a reject stream containing concen-
trated contaminants. Typically, as finer particles are removed, the
purification process becomes more water- and energy-intensive.
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. Systems that deliver a higher wa-
ter quality than the facility needs will often be more expensive to
operate than a more appropriate system and can result in wasted
water and energy.
There are several technical standards for water quality that facili-
ties can use to evaluate the appropriate water purification method,
including ASTM International
ASTMD1193 Standard Specification
for Reagent Water
and the International Organization for Standard-
ization (ISO)
ISO 3696Water for Analytical Laboratory Use—Specifi-
cation and Test Methods
.
These standards generally classify water
quality into specific types based on the quality required.
3
When determining the level of treatment needed to supply water of a specific qual-
ity, there are a number of water purification technologies used in lab and medical
facilities that can be considered. These include: microporous filtration, carbon filtra-
tion, deionization, distillation, membrane processes, and water softening. 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 contaminants can be tolerated.
Microporous Filtration
Microporous filtration physically removes solid contaminants by capturing them on
the surface of the media. Microporous filtration typically occurs at low pressures and
does not remove any dissolved solids.
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After a period of use, filters will require back-
washing with water to remove contaminants trapped on the media surface.
Carbon Filtration
Carbon filtration uses adsorption to attract particles as water passes through the
filter. The adsorption process depends upon the physical characteristics of the
activated carbon; the chemical compositions of the carbon and the contaminants;
3
Millipore. Overview of LabWater Grades.
.
4
Messinger, Stephen. September 2006. “What Makes Water Taste Best?”
Water Conditioning & Purification Magazine
.
.
Water purification system in a laboratory
