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Fig 1. Multi-step purification process required to achieve different water quality levels. All images courtesy of Millipore.
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Designing a new lab water system or retrofitting an existing system requires a thorough
understanding and working knowledge of common and emerging contaminants, purification
technologies, industry standards, user requirements and water distribution options.
Selecting the purification technologies, materials, design, and installation configurations
best suited to individual user and departmental needs throughout the facility can be a daunting
task. Further complicating the design of a lab water system are usage patterns and purity
requirements that can vary widely among labs, floors, and departments within a single
facility.
Before embarking on the design of a customized lab water system, a number of key areas must be
thoroughly defined:
- Who: Who needs access to pure water?
- What: What volume and purity are needed, and what unique contaminants, if any, must
be addressed?
- When: When is the water needed, and when does peak demand occur?
- Where: How will the water get to where it needs to go?
This article describes key factors to be considered when designing a customized lab water
system and outlines best practices for defining purity level and volume requirements. Options for
water distribution design and equipment are also described.
Getting started
The foundation of a successful lab water system design is a clear and precise definition of user
needs throughout the facility. The purity level and volume of water required at each point of use
can vary considerably and therefore must be fully assessed to properly guide the system
design.
A number of organizations offer detailed standards for water purity levels. While there is some
variation across these standards, most classification schemes define three purity levels: Type I,
Type II and Type III, with Type I being the most pure (Table 1). When assessing user needs, keep
in mind that different laboratory applications require different types of purified water (Table
2). General or “non-critical” applications such as rinsing glassware typically require Type III
water; more sensitive research applications require Type II or Type I.
Table 1: Summarized guidelines of water
quality standards.
All tables courtesy of Millipore. |
| Contaminant |
Parameter and
unit |
Type
III |
Type
II |
Type I |
| Ions |
Resistivity MΩ. cm |
> 0.05 |
>1.0 |
>18.0 |
| Organics |
TOC (ppb) |
<200 |
<50 |
< 10 |
| Pyrogens |
(EU/mL) |
NA |
NA |
<0.03 |
| Particulates |
Particulates >0.2 um (units/mL) |
NA |
NA |
<1 |
| Colloids |
Silica (ppb) |
<1000 |
<100 |
<10 |
| Bacteria |
Bacteria (cfu/mL) |
<1000 |
<100 |
<1 |
Once water purity requirements are defined, the design team must calculate the volume of water
required at each use point. This calculation must reflect all use points requiring pure water,
including sink faucets and instruments such as autoclaves and glassware washers. Timing of water
usage must also be determined. Will usage be relatively consistent over a typical workday, or will
demand spike during the day? Water may be required over a 24-hr period or limited to an eight-hr
workday; there may also be demand for water on weekends.
When assessing volume requirements, estimate the maximum simultaneous usage across the multiple
points of use. This information provides guidance regarding the proper size of equipment, flow
rates and pressure requirements.
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Fig. 2. Key elements of a water purification system.
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Purfication technologies
Proper design of a water purification system requires a customized combination of purification
technologies and system components to achieve the necessary water quality and capacity for all
facility applications.
The four major categories of contaminants (inorganics, organics, microorganisms and
particulates) found in tap water can occur naturally or may stem from substances added at water
treatment facilities, from man-made compounds, or from materials contained within systems used to
distribute water.
Since no single technology can remove 100% of the contaminants commonly found in tap water, lab
water systems must incorporate a combination of technologies to produce purified water. Table 3
summarizes the most commonly used water purification technologies and their effectiveness in
removing these contaminants. Fig. 1 illustrates a multi-step purification process required to
achieve different water quality levels starting from tap water.
Designers of lab water systems must also be aware of the possible presence and impact of
“emerging contaminants” in the water supply. Emerging contaminants are substances characterized by
a real or perceived threat to human health or the environment for which there is no published
health standard or a standard is currently being developed. These substances can include
nanoparticles, pharmaceuticals, personal care products, endocrine disrupting compounds (EDCs),
perchlorates, and chemicals used in products and packaging.
Analytical laboratories monitoring the presence of such emerging contaminants must ensure that
their laboratory water is purified to the highest degree possible, so that even minute amounts of
contaminant in the purified water do not interfere with trace-level analyses. Other labs that
require a similar standard of purity are those that develop sensitive methods for the detection of
emerging contaminants and their metabolites in various matrices, and those that focus on toxicity
testing. Emerging contaminants may also have an impact on cell-based or other biological
assays.
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Table 2. Different water purity levels are required for different applications.
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In many cases, standard lab water systems can effectively remove such contaminants from tap
water. There are cases, however, when additional purification steps must be added to the regimen
to ensure removal. For example, Millipore has developed a point-of-use cartridge containing a
specific type of activated carbon optimized for the removal of EDCs. Water purified using a
combination of technologies commonly used in Millipore water purification systems, with the
addition of the specific carbonaceous point-of-use cartridge, contained no measurable amounts of
EDCs such as phthalates and dioxins.
System components
Water purification system components (Fig. 2) can be customized to meet facility requirements and
maximize user convenience. These components include:
- Make-up water purification system. The makeup water purification system produces the
total volume of water expected to be consumed by an individual user, department or (in the case of
a larger central system) the complete facility each day. The make-up system starts with tap water
and purifies it to a level that meets predefined quality requirements.
- Storage reservoir. Purified water from the makeup system is stored in the reservoir
to help cover peak periods of high demand. The make-up system and the storage reservoir must be
sized together to meet the daily pure water demands.
- Delivery and distribution of pure water. Pure water from a larger central system will
require a distribution pump, additional purification equipment to maintain water quality, and
distribution loop piping to bring water through a facility to use points at the correct flow rates
and pressures. Small individual systems need to include point-of-use dispense points to
conveniently deliver water.
- Point-of-use delivery and polishing. Water that is accessed from the distribution
loop via multiple point-of-use locations can include additional polishing at delivery points to
increase water quality to meet the needs of more sensitive applications. Small individual systems
may include polishing integrated into the system to increase water quality.
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Table 3. Effectiveness of various purification technologies in removing common water contaminants. Circles indicate the relative effectiveness of removal; a full circle is approximately 100% removal of the contaminant.
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Careful consideration must be given to selection of the production rate of the make-up
purification system, the volume of the storage reservoir, and, specifically, how the pure water
will be delivered to the points of use. A properly designed system will satisfy all the customer’s
water demands--including the peak demand--with the water “turning over” frequently to avoid
stagnation and minimizing risk of contamination.
Configuration options
The overall configuration of a system used to provide pure water throughout a lab facility can be
customized in a number of ways to meet unique needs.
The traditional design approach has been to lay out a single loop with several hundred or
thousand feet of pipe throughout a facility, with a larger single water purification system,
storage tank, and distribution pump in a central location (Fig. 3). However, several alternative
configurations exist for the design of a total pure water system. Considering these alternative
approaches can help identify the design that will best meet the needs of the facility.
A simple variation of the central location pattern may include duplex make-up purification
systems or distribution pumps. This approach provides redundancy of key components, which allows
one system to shut down for routine maintenance or service while the other remains
operational.
When volume and purity requirements vary widely within a facility, the water system can be
configured by floor or by department with smaller systems designed to meet “local” user
requirements. A large system with a separate distribution loop can address areas where high-volume
needs exist (such as a central glassware washing station), while other departments or floors can
be addressed via smaller systems and smaller distribution loops (Fig. 4).
Small, point-of-use systems can also be incorporated to meet individual user or laboratory
needs for ultimate flexibility (Figs. 5 and 6). These systems include a local purification system,
storage and additional polishing to meet water quality requirements. This approach eliminates the
need to extend central piping to all departments and can vastly simplify the main total water
purification system. In some cases, a facility’s pure water requirements can be met using only
multiple small point-of-use systems, completely eliminating of the need for distribution
piping.
Optimizing system configuration
A wide range of configuration options must be evaluated and customized when designing a lab water
purification system that effectively meets user needs. The article beginning on page 00 describes
the key factors to be considered to ensure a successful design and outlines best practices for
defining purity level and volume requirements. Options for water distribution design and equipment
are also described.
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Fig. 3. Central system configuration with distribution throughout the whole facility.
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User requirements and a facility’s overall layout will guide selection of the optimal
distribution pattern. Options for configuring lab water distribution are outlined below, with a
description of the advantages and limitations of each.
General recommendations
When considering lab water system configurations, a number of general recommendations should be
followed:
- Avoid long distribution loops to minimize the bacteriological risks.
- Consider horizontal distribution (one or two floors) instead of vertical distribution (over
several floors), to minimize pressure-drop-related issues and optimize the linear velocity of
water in the pipes.
- Remote locations should be fed with a dedicated system rather than extending a distribution
loop; this solution is more economical and guarantees better results.
- Duplex configuration water purification modules and distribution pumps should be considered to
provide redundancy (designed in back-up) when continuity of water supply is critical for the
users.
- Production system selection should be based on volume, water quality and quality monitoring
facilities.
- Storage and distribution system design should take into account number and location of points
of use; individual department, quality and volume needs; and any high-volume usage points.
Single loop configuration
The traditional design approach to supplying pure water has been to lay out a single loop, with
piping placed throughout a facility. A larger, single water purification system, storage tank and
distribution pump are centrally located (Fig. 3). A number of disadvantages exist, however:
- Risk of drop in water quality between loop supply and loop return if the distribution loop is
long.
- Limited departmental control over water supply.
- Risk of water shortage if any issue occurs in the production system or distribution loop.
- Increased pressure drop in a single long distribution loop, requiring high pressure after the
distribution pump.
- Potential flexibility issues if needs change or the facility is reorganized.
- One quality for the whole building = a higher running cost for applications that require a
lower grade of purified water.
- General system maintenance (sanitization) requires all labs to stop using water.
A simple variation of the central location pattern may include duplex make-up purification
systems or distribution pumps. This approach provides redundancy, allowing one system to shut down
for routine maintenance or service while the other remains operational.
Several alternatives to the central system configuration exist, however. Depending on client's
needs, constraints and expectations, the designs described below will suit most situations and
offer important advantages.
Departmental or floor-by-floor
When volume and purity requirements vary widely within a facility, the water system can be
configured by floor or by department, with smaller systems designed to meet “local” user
requirements. A large system with a separate distribution loop can address areas where high-volume
needs exist (such as a central glassware washing station), while other departments or floors can
be addressed via smaller systems and smaller distribution loops (Fig. 4).
The advantages of a “by floor” or “by department” approach include the following:
- Each department floor has some control over its water supply.
- Limited distribution loop length enables optimum water quality to be maintained in the
loop.
- If one production module or distribution loop is down, other points of use are still
operational. A bridge between loops could facilitate this.
- Some flexibility exists if the loop needs to be extended or adapted to new users.
- The production and storage unit can be tailored to volume and quality needs by floor or
department.
Running costs are optimized since each department gets exactly what it needs. But the initial
investment is higher, and more than one location must be maintained.
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Fig. 4. Floor-by-floor or department-by-department system design.
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Point-of-use systems
Small, point-of-use systems can also be incorporated to meet individual user or laboratory needs
for ultimate flexibility (Figs. 5 and 6). There are several options for final point-of-use
polishing that combine the necessary purification technologies to meet quality requirements of
critical applications. Monitoring resistivity and total oxidizable carbon (TOC) levels should be
included as a final check of water quality.
These small point-of-use systems include a local purification system, storage, and additional
polishing to meet quality requirements. This approach eliminates the need to extend central piping
to all departments and can vastly simplify the main total water purification system. In some
cases, a lab facility’s pure water requirements can be met using only multiple small point-of-use
systems, without the need for any distribution piping.
A lab water system design structured by department and incorporating point-of-use modules
provides the ultimate in flexibility and offers important advantages:
- Each department has complete control over its water supply.
- A limited loop length enables optimum quality to be maintained in the loop.
- If one production module or distribution loop is down, other points-of-use are still
operational. A bridge between loops could facilitate this.
- Complete flexibility exists if the loop needs to be extended or adapted to new users.
- Maintenance procedures are limited to simply changing purification packs.
In terms of overall costs, the point-of-use approach can be less expensive than a loop
configuration when all loop-related expenses are considered. However, if all labs are in close
proximity to each other, this solution could necessitate a higher investment than a loop. Less
downtime is usually experienced with point-of-use systems, and this helps to maintain a lab’s
productivity.
Driven by user requirements
A successful lab water system design and installation depends on a clear definition of user
requirements and an understanding of current and possible future occupancy and usage patterns. The
following scenarios represent actual projects, each with different needs and solutions.
Scenario 1: New multistory building with labs on two floors. Primary functions are
teaching and research. Occupancy of lab space is expected to increase. Type II water is required
by all labs, with several use stations requiring Type I ultrapure water. Total facility demand is
between 2,500 and 3,500 L/day, Monday through Friday, 7a.m. to 6 p.m., with periodic low demand
during off hours.
Double make-up systems and distribution through the entire facility was the selected
configuration strategy. A single central system was chosen to feed two separate distribution
piping loops, one dedicated to each lab floor. The need for pure/ultrapure water was met by direct
feed to small glassware washers, pure water facets and point-of-use Type I polishing systems. Type
I polishing systems were to be added as needed with increased building occupancy.
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Fig. 5. System design by floor or by department with some small specific individual systems.
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Scenario 2. Two-story building with multiple labs on both floors. The primary
functioin is R&D, with support labs making up 75% of facility space. Type II water is required by
all labs, with several use stations requiring Type I ultrapure water. The total facility demand is
1,400 to 1,500 L/day. On Floor 1, use is estimated at 1,200 L/day peak demand, with 750 to 800
L/day typical. On Floor 2, peak demand is estimated at 300 L/day peak demand, with 200 L/day
typical.
Floor-by-floor systems were chosen for this facility, combined with a smaller point-of-use
system. This configuration was chosen because 75 to 80% of total demand came from Floor 1, with
relatively low demand from Floor 2. Floor 1 included a central system design with distribution
piping to use points; Floor 2 included several individual systems to meet specific pure water
volumes and quality. There was no distribution piping on Floor 2.
Type II direct feed was provided to glassware washers, pure water faucets for general rinsing
and non-critical solutions, buffers and reagents; direct feed to point-of-use Type 1 polishing
systems is used for sensitive analytical instruments and critical reagent preparation.
Scenario 3. Two-story facility with labs on both floors. Type II water is required by
all labs, with several use stations requiring Type I ultrapure water. Total facility demand is
estimated at between 1,500 and 2,000 L/day, Monday through Friday, 7 a.m. to 6 p.m., with periodic
low demand during off hours.
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Fig. 6. Lab water system incorporating small point-of-use systems to maximize flexibility.
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Two options were investigated for this building. One choice was a central system with
distribution piping providing water to sink faucets, with Type I polishing systems at several
locations. The other choice was just locating several individual tap-to-ultrapure systems
throughout the facility.
The ultimate decision was to use individual tap-to-pure-ultrapure systems, based on the
client’s desire to avoid distribution piping installation and preserve flexibility to move and/or
add individual systems in the future. Type II direct feed goes to glassware washers, pure water
faucets for general rinsing and non-critical solutions, buffers and reagents. Direct feed is
routed to point-of-use Type I polishing systems for sensitive analytical instruments and critical
reagent preparation. Instrument-feed quality is required by one clinical chemistry analyzer and is
addressed by an additional tap-to-pure system.
For additional case-study examples, see the “Total Water Solutions Guide”at
www.millipore.com/A&E.
Control and coordination of all operating modes, performance parameters, water quality,
indicators for routine maintenance, and key alerts and alarms for the total system–from makeup to
distribution–also need to be part of the overall system design. Easy and user-friendly access must
be provided to the controls and displays for simplified, convenient system operation, monitoring
and maintenance. Monitoring water quality at key stages throughout the system is essential for
confirming proper functioning and final water quality.
As a final step, it is important to prepare detailed documentation that includes user
requirements, equipment specifications, total system design, control and monitoring, and system
performance. This documentation must be reviewed with the principals of the project to ensure
complete alignment between user requirements and the proposed final design.
Conclusion
In conclusion, purified water is the most common reagent found in lab facilities, used throughout
experimental protocols in virtually every type of application. Whether used for washing glassware,
buffer preparation, cell culture or a highly sensitive analytical technique, the appropriate grade
of water is essential to support research projects and maintain productivity.
A well-designed lab water system can help ensure the success and integrity of research for all
types of facilities, from the smallest academic labs to the largest research building.
Successful water purification systems effectively align purification technologies, mechanical
components and installation options with user needs throughout the facility. Designing the optimal
system begins with a thorough understanding of user requirements, usage patterns and facility
layout. A wide range of configuration options can then be evaluated and customized to create the
optimal system.
Jeffrey Denoncourt is custom water systems manager at Millipore, Billierica, Mass., which
makes pure and ultrapure water systems and offers related services. Visit www.millipore.com/A&E to
access the new “Total Water Solutions Guide,” which includes a range of content for architects and
engineers who design laboratories.
Published in Laboratory Design newsletter: Vol. 15, No. 10, October, 2010
