Specification is Key to Optimal Water Purification

Water quality, grade and maintenance are important factors to consider when specifying a centralized reverse osmosis water purification system.

Choosing, operating and maintaining a reverse osmosis (RO) system should be straightforward. So what are the specific problems that prevent the best results from being achieved in the lab? In short, the specification sometimes fails to match the application, while in other cases it is simply that efficiently processed pure water is incorrectly used. Either way, it’s a lack of knowledge that’s the stumbling block.

As legislation tightens across the globe, an awareness of the latest technology is key, and obtaining advice and equipment from approved sources is often the only way to meet requirements. Water quality standards are stringent and it is vital that the pure water systems used meet these exacting standards consistently, and at the right volume required to function effectively and efficiently.

A series of key issues need to be considered by technicians and laboratory staff when choosing an appropriate water purification system. Armed with this knowledge, the latest technology can then be specified to help improve water quality and laboratory productivity.

Laboratories need a dependable and consistent supply of pure water on demand, whenever and wherever technicians require it. For small laboratories that typically require no more than 300 L of purified water per day, a variety of easy-to-install and maintain standalone units are available that offer a simple and cost-effective means of providing purified water direct from a mains water supply.

For larger laboratories, a centralized RO system generally becomes the most economical method of providing a constant supply of pure water quickly and efficiently at the point of use. This is generally because requirements, in terms of quantity and grade of water, can vary between departments. In many establishments, pure water has to be fed to a number of points of use that can be spread over various floors within a building.

Prior to specifying a centralized plant, however, whether it is for a new building, a replacement or an upgrade to an existing system, there are several key factors that must be taken into consideration. Quantity of water and patterns of use, the grade of water required at various points of use and ongoing maintenance are some of the key issues that can affect the specification and ultimate performance of a water purification system.

Quality and grade

To ensure that any centralized system meets the unique requirements of a laboratory, one of the most important elements to consider during specification is the quantity of water needed. This must be considered in terms of the peak instantaneous demand and the pattern of use throughout the working day. While it is easy to predict the maximum requirement at each take-off point, the likelihood of all points being in use at the same time has to be given some consideration, and this is where an estimate must be made as to the probable number of points in use at any one time (known as diversity).

The quality or type of water required at each point of use also needs to be defined. For specialist applications, such as ion chromatography, atomic absorption, tissue culture and molecular biology work, water of the maximum theoretical purity (18. 2 MΩ. cm) may be required. This eliminates the risk of spurious results that can be obtained should there be trace contaminants present in the water.

In terms of specification, it is essential to understand the balance between the types of water required; in many instances, the requirement for ultrapure water can be as little as 10 L per day. In terms of system design, it is essential that the system itself is designed to meet the majority of demand.

Maintenance

Once a centralized plant has been specified and commissioned, it is then important to ensure that the system is regularly serviced and maintained as required. Without the necessary ongoing maintenance, it is virtually impossible to preempt potential problems, resulting in the possibility of considerable downtime and cost. Similarly, consideration should be given during the system design to when maintenance can be performed, so that redundancy or storage capacity is included to minimize disruption to laboratory users.

Typical routine maintenance can include checking the RO pretreatment equipment and replacing filter elements and other consumables as required. Furthermore, the reverse osmosis membranes generally require chemical cleaning every 3 to 6 months, depending on usage, to remove organic material, bacteria and scale deposits, which inevitably build up during use. To maintain microbiological integrity, it is normal for the system to be chemically sanitized on an annual basis. Without these housekeeping and maintenance procedures, the system will not operate at optimum performance, which will ultimately affect running costs and water quality.

Increasingly, laboratories are turning to the system manufacturer to provide preventative maintenance on a planned basis. It is essential, however, that any organization that provides maintenance cover for centralized plants offer a highly flexible service that meets the unique requirements of the system. For example, usage can significantly affect maintenance issues in terms of service intervals and the requirement for consumables. Furthermore, companies like Purite can offer a 24/7 service contract to ensure that, in the unlikely event of a problem, a locally based qualified engineer can provide assistance and support.

There are many factors to consider when specifying and installing water purification equipment, but the performance and successful operation of any RO system depends on the quality of the equipment and installation, and on the ability of the end user to monitor a number of simple, but key, process parameters on a regular basis. By working with a supplier who is willing to assist on-site and help users specify the best solution for their needs, their efforts will be rewarded with the most efficient, economical and reliable supply of purified water for specific laboratory requirements.