Simon Charlesworth, Laboratory Sales and Marketing Manager at Purite, discusses the importance of correctly specifying a water purification system for a laboratory and highlights how the latest technology has benefited the pathology department of a leading NHS trust.

Purified water is essential in a wide range of laboratory applications, with varying degrees of purity required for different purposes. While routine processes such as glassware cleaning may demand a relatively low level of purification, for other applications including analytical experimentation and testing it is absolutely critical that the optimum level of water purity is achieved. The latest generation of water purification technology is enabling pure water to be accessed easily and cost effectively throughout the laboratory. 

British Standard, BS EN ISO 3696, defines three measurable Grades of water purity for use in defined laboratory applications.

The lowest level of purity, Grade 3, required for general use in laboratories, is produced using an effective purification processes called reverse osmosis (RO) where a pre-treated potable water supply is fed under pressure into a module containing a semi-permeable membrane. The membrane removes a high proportion of impurities, including up to 98% of inorganic ions, together with virtually all colloids, micro-organisms, endotoxins and macromolecules, in a residual concentrate stream that is run to drain.

For Grade 2 water, required for applications such as glassware cleaning, a combination of RO and deionisation (DI) is often used, with water making a single pass through the system. Likewise, to achieve Grade 1 water, the highest level of purity defined by BS EN ISO 3696  used in applications such as ion chromatography and clinical analyser feed, a similar process is used, but, in this instance, water is continually circulated and polished through the DI resin until the required level of purity is reached.

A process known as continuous- or electro-deionisation (CDi or EDi) is often used by larger integrated systems in place of resin deionisation to produce Grade 2 water, however, smaller desktop systems incorporating ion exchange resins in disposable cartridges can provide a more economic and convenient solution. Additional processes, such as UV disinfection and sub-micron (typically 0.2 microns) filtration can also be used where Grade 1 water with enhanced microbial quality is required.

As it is essential that pure water used in the laboratory complies with these standards and is accessible to technicians wherever it is needed, those responsible for installing water purification systems are faced with the choice between a number of self contained individual units at different positions throughout the laboratory, or an extensive ringmain distribution system, which needs to be integrated carefully into a lab’s design. In practice, larger laboratories will often install a ringmain with Grade 2 or 3 water being recirculated, with additional polishing at the point of use, if required.

The latest generation of water purification technology, from manufacturers such as Purite, includes solutions ranging from small units that can sit on a worktop or be wall mounted, and provide small quantities of purified water, to standard or custom built systems offering large volumes of water for routine use. To ensure that the system you choose is the most suitable solution for your laboratory it is necessary firstly to understand exactly what your purified water requirements are or will be. Working closely with an experienced supplier can enable you to build a solution specifically designed around your laboratory, saving you from having to make costly compromises to accommodate a standard system. It is important to consider if the required volume of pure water is consistent or if there are intermittent periods where particularly high volumes of water are required, such as the filling cycle of a glass washing machine, followed by a relative lull in usage. This analysis of the patterns of daily usage is vital, as technicians often only look at total consumption levels, over a daily, weekly or monthly period, with the result that systems are over sized and used at less than optimum capacity for the majority of the time. Over sizing a system takes up valuable space unnecessarily and can have a negative effect on the performance of a reverse osmosis system. Similarly, an estimate should be made of the likely number of points that will be in use at any one time; if it is simply assumed that all points will be in use at once, the resulting system can be hugely over sized.

Additionally, it is advisable to take into account the ease of maintenance for a water purification system. Routine cleaning and maintenance are essential if the highest levels of performance are to be obtained from any system and components such as RO membranes are to offer optimum service life. Therefore, a system should be chosen that requires the lowest possible amount of downtime, in order to maximise productivity and avoid disruption. The cost of consumables should also be kept in mind, as systems that use high volumes of resins, chemicals and cleaning solutions can quickly become uneconomical.

An example of how the latest purification technology can benefit a laboratory can be seen in one of the leading NHS trusts in the country, which recently installed a self-contained Purite water purification system as part of an ongoing development programme to improve the performance of its blood analyser test units. The pathology department at the hospital was looking for a water purification system that was reliable and efficient, adaptable to its existing analyser, low maintenance, and that would deliver consistent results, providing high quality water at a realistic cost.  The blood analyser, which can automatically perform a range of clinical tests including complete blood cell counts, detection of acids or viruses, and quantification of glucose, all in a matter of seconds, has become an integral diagnostic tool set for the hospital. In order to give patients a reliable service and expert advice, doctors and clinical staff must be able to rely on the blood analyser test results, which is why a Purite system was selected to provide Grade I quality water for the sterilisation of cuvetts, probes, dilution and reaction cups, and onboard probes within the analyser.

The system chosen by the laboratory uses a Prestige Descale Reverse Osmosis unit to remove up to 95% of dissolved Calcium, Magnesium and Sodium salts,  as well as > 99% of bacteria; an exchangeable deionisation cylinder is also incorporated to polish the water further and remove the remaining 5% of residual salts. This ensures that the water quality is consistently in excess of Grade 1. In addition, a separate ultra-violet disinfection unit is incorporated in the ringmain distribution system to ensure that disease-causing micro-organisms such as E. coli are neutralised. The system is completed by a 0.2µm bacteria filter to remove fine particulates and microbial contaminants.

To minimise maintenance and optimise productivity the Prestige Descale unit contains a built-in microprocessor control system that constantly monitors system performance and water quality. This automatically responds with specific alarm messages prompting action if levels exceed predetermined parameters, to protect the unit from damage. This particular application highlights the critical importance of selecting the most effective water purification technology, and shows that with a good understanding of a laboratory’s requirements, a bespoke system can be built cost-effectively that is reliable, easy to use and needs very little attended operation, freeing clinical staff to concentrate on patient services.