Pure Water
A successful water system design begins with 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 in order to properly inform the designer of the water purification system.
What to Consider When Designing a Customized Lab Water System
Purified water is the most common reagent found in laboratory 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 vast array of purification technologies, materials, design, and installation options are available to deliver purified water throughout a laboratory facility. Identifying the combination best suited to meeting individual user and departmental needs throughout the laboratory 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.
This article describes several key factors that must 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.
Where to begin?
Designing a new lab water system or retrofitting an existing system requires a thorough understanding and working knowledge of contaminants, purification technologies, industry standards, user requirements, and water distribution options.
A successful water system design begins with 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 in order to properly inform the designer of the water purification system.
A number of organizations offer detailed standards for water purity levels. While there is some variation across these standards, most classification schemes have three purity levels—Type I, Type II, and Type III—with Type I being the most pure (Table 1). When assessing user needs, it is important to keep in mind that different laboratory applications require different types of purified water (Table 2).
Once water purity requirements are defined, it is essential to calculate the volume of water that will be required at each use point. This calculation must take into consideration all use points requiring pure water including sink faucets and instruments such as glassware washers. Timing of water usage must also be determined. Is the expected usage relatively consistent over a typical workday or are there times of peak demand? Will water be used over a 24-hour period or limited to an eight-hour workday? Will there be demand for water on the weekend?
When assessing volume requirements, it is also important to estimate the maximum simultaneous usage when there are multiple points of use. This information provides guidance as to the proper size of equipment, flow rates and pressure requirements of the water system designed for the facility.
Pure water supply configuration options
The overall configuration of a system used to provide pure water throughout a laboratory facility can be customized in a number of ways in order to meet that facility’s unique needs.
The traditional design approach to supplying pure water to a facility 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 (Figure 1) (Click the image to enlarge).
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 these 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 (Figure 2) (Click the image to enlarge).
Small, point-of-use systems can also be incorporated to meet individual user or laboratory needs for ultimate flexibility (Figures 3 and 4) (Click the images to enlarge). These small point-of-use 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 laboratory facility’s pure water requirements can be met using only multiple small point-of-use systems, eliminating completely the use of distribution piping.
Purification system selection and design
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 be naturally occurring, substances added at water treatment facilities, man-made compounds, or derive from materials contained within systems used to distribute water.
Since no single technology can remove 100 percent of the contaminants commonly found in tap water, lab water systems must incorporate a combination of approaches to produce purified water. Table 3 summarizes the most commonly used water purification technologies and their effectiveness in removing these contaminants. Figure 5 illustrates a multi-step purification process required to achieve different water quality levels.
In addition, 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.
Various components of the water purification system should be customized to meet facility requirements and maximize user convenience. These components include:
- Make-up water purification system
The make-up 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 make-up 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.
Conclusion
A well-designed lab water system can help ensure the success and integrity of research from the smallest academic labs to the largest research laboratory buildings.
Successful water purification systems effectively align purification technologies, mechanical components, and installation options with user needs throughout the laboratory 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.
Visit www.millipore.com/A&E to access Millipore’s new “Total Water Solutions Guide”.