Lab water, purified by any of a number of means, is a vital resource in most laboratories. Purified lab water ranges from Type I, which is suitable for analytical tests requiring minimal interference and maximum precision and accuracy, through Type II for analytical tests in which the presence of bacteria can be tolerated, to Type III, which is suitable for general washing and for use as feedwater for producing higher grade water, as well as bacteriological media preparation. A fundamental principle when seeking to improve the purity of your lab water is to ensure that the correct grade of water is used for the appropriate application.
This MindMap explores some of the different options available for improving the purity of lab water by taking into account the specific needs of your own lab and that of the labs around you.
Improve the purity of water in my lab
Reduce storage times
Pure water that is not recirculated is at risk of significant deterioration in quality and bacterial growth. Storage of pure water should be kept to an absolute minimum in order to reduce this risk.
Use a multi-stage process
Most water purification systems rely on more than one process to achieve the desired level of purity. Installing a system that uses a primary treatment followed by a ‘polisher’ is a common method of achieving water of the required purity. Water should be constantly circulated through the entire system to avoid recontamination.
Undertake regular service and maintenance
All water purification systems require some form of ongoing maintenance, from the cleaning and changing of filters to the replacement of larger parts. Some systems require servicing from an outside expert, while others can be maintained by users by simply replacing cartridges, for example.
Opt for a regular maintenance contract
Arranging a contract with a supplier for regular servicing of a water purification system is a cost-effective way to ensure that the system performs optimally at all times and is likely to give more years of service.
Choose a system that requires minimum servicing
Some systems are designed so that they can be easily maintained by users or lab managers with minimum input from outside experts. These systems use cartridges, for example, that can easily be changed to provide new filters.
Replace parts as necessary
Although water purifiers do not have moving parts, some components such as filters, UV lamps, and extraction filters will need to be changed periodically to maintain optimum performance.
Consumables that need to be replaced on a regular basis to ensure optimum performance include filter units and cartridges.
Purchase spare parts
Spare parts for water purifiers can be purchased new from the manufacturer. Although the trade in second-hand parts for water purifiers is not on the same scale as for some other laboratory instruments, it is possible to buy used parts in some cases as a cost-effective alternative to new parts.
Implement staff training
All staff who need pure water as part of their everyday tasks should be trained on whatever system is available in the lab to make sure that they are using it properly and obtaining the necessary level of purification every time.
Training in the effective use of pure water is provided by a number of commercial training companies, either as part of a general laboratory training program or as a specific course in water purification. Many of the larger manufacturers of water purifiers also supply training in their systems, either on site or on-line.
Monitor water purity regularly
Water purity should be measured routinely using specialized monitoring kits. This allows any deviation away from the required standard to be quickly identified, preventing contamination of experiments and allowing the problem to be rectified before it escalates. NIST standards specify a resistance of >1, >18, and >18,2 megohm.cm for water Types II, I and I+ (ultrapure water), respectively.
Upgrade or invest in new
Most labs have some form of water purification already installed. One of the fundamental questions when seeking to improve water purity is whether to upgrade the existing system, which can be cost effective, or whether to install a completely new system, which may give more satisfactory results.
Centralized or point-of-delivery system
If the decision is made to invest in a new system, the next decision should be whether this will be a centralized system or a point-ofdelivery system, which delivers pure water as required on-tap.
Point-of-use systems are gaining in popularity due to lower installation costs and the greater control and flexibility offered. These systems also tend to require less lab space, typically operating from a small tank stored under a bench.
Centralized systems can be costly to install and, because they operate all night and over the weekend, can be expensive to run. In addition, it can be difficult and costly to maintain a high level of purity in a central system, the water quality can deteriorate over time and if the system goes down, the whole floor or building’s purified water supply goes down.
Take extra care when pure water is used sporadically
Always allow the pure water to run for a certain period of time after inactivity. For example, allow at least 5 liters of purified water to drain after the weekend or holidays, particularly when using the water for critical applications.
Select appropriate water purity
Water purification is a costly business, and the lowest acceptable level of purification should be used for all applications to save wastage. For example, all glassware rinsing should be performed using Grade III water.
Choose appropriate purification technique
Most water purification systems use a combination of processes to remove relevant contaminants:
1. Distillation - Excellent for removing particulates, microorganisms, pyrogens
2. Deionization - Excellent for removing dissolved solids, dissolved gases
3. Reverse osmosis - Excellent for removing particulates, microorganisms, pyrogens
4. Activated carbon filtration - Excellent for removing dissolved gases, dissolved organics
5. Microporous filtration - Excellent for removing particulates, microorganisms
6. Ultrafiltration - Excellent for removing particulates, microorganisms, pyrogens
7. Ultraviolet oxidation - Excellent for removing particulates, microorganisms, pyrogens
Focus on contaminates of greatest concernFocus on contaminates of greatest concern
The five types of contaminants that may be found in water are:
2. Dissolved inorganics (solids and gases)
3. Dissolved organics
Ensure that the water purification system you employ in your lab is designed to eliminate those contaminants that are of major concern in the particular techniques and processes common in your lab.
Consider desired application
Common lab applications tend to have their own requirements in terms of purification. For example:
Polymerization of PTFE requires removal of particulates
HPLC requires removal of all dissolved organics
Healthcare and pharmaceutical applications require removal of all microorganisms and pyrogens
GC-MS requires ultrapure water for trace analysis
DNA/RNA applications require ultrapure water
Undertake a specialist lab audit
Installing a new water purification system is a costly enterprise and can be time-consuming and complex. Most suppliers of pure water systems offer a consultancy service to help you select the appropriate system for your own needs and to suit your own budget. Treat the advice of sales reps from large catalogue distribution companies with caution as they tend not to know the system as well as the manufacturers themselves. Also, avoid becoming tied into proprietary technology when purchasing a new system, as the processes used are standard across all systems and need not be complex.
Consider contamination post-dispensing
The purest water instantly becomes at risk of contamination once it is exposed to the air. As well as considering the water purification system itself, consideration should be given to techniques to maintain water purity once it is in use, otherwise all the effort expended in attaining high-purity water is wasted.
For example, pure water should always be used in glassware that has itself been cleaned thoroughly to remove contamination, then rinsed with pure water; it should be used in a closed environment to prevent contamination from the air; and it should be used quickly once it has been dispensed to reduce the risk of contamination.