10 ANALYTICAL AND LABORATORY EQUIPMENT
technology used to produce it. A surprisingly common scenario, for example, is to see technicians storing or transporting the purified water in open plastic containers. Storing water for long periods after treatment increases the risk of contamination, so while it is important for labs to size their purification system to meet both current and expected future water needs, care should be taken not to significantly oversize the system. Where demand variability is high, it can be useful to select a system that features built-in recirculation to maintain the quality of water stored in internal tanks. Even the best water
purification systems will only perform well when supported by routine cleaning/disinfection and maintenance, and so to maximise efficiency labs should look for equipment that is straightforward to maintain, with easy to change consumable parts. Modern
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systems have made major strides in the area of usability. Tey may, for example, employ the use of colour indicators in ion exchange systems that provide a simple but clear visual indication that it is time to change the resin, or feature digital displays to indicate flow rates, overall water quality, specific contaminant levels and the condition of consumables. On-board data logging capabilities are also built into many higher-end systems, allowing operations and maintenance staff to monitor their performance over time. Regular cleaning of RO membranes is relatively straightforward and is typically carried out using specialised cleaning solutions. Acid-based cleaners are used to remove scale, and alkaline based solutions to remove organic matter. If required, special chemicals can be used for disinfecting, but should only be added once all scale and organic matter has been removed.
Solutions are simply circulated through the RO system and tank, and then flushed to drain. Te cost of consumables is also an important consideration when comparing different options, as systems that use high volumes of resins, chemicals and cleaning solutions can quickly become uneconomical. Energy costs can vary considerably too, with the better systems able to save energy by putting pumps into standby mode when there is sufficient water in on-board storage tanks to meet current demand.
Laboratories will need to decide if they want to handle routine maintenance themselves, or enter a service agreement with their chosen provider. Whichever option they select, they will need to ensure they have service arrangements in place to suit their needs, for example ensuring that support is available overnight or at weekends to ensure continuity of supply.
Above left: Lower-volume applications can rely on point- of-use water systems
Above right: Some lab tests may require far higher levels of purity than others
Mark Bosley is with Suez Water Purification Systems.
www.purite.com
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