While on the one hand, sustainable processes and operation have become increasingly important for laboratories around the world, on the other, these same labs often require ever greater pure (Type 2) water quality. To achieve the desired level of pure water quality, laboratories rely on water purification systems to remove contaminants that are initially present in water, such as ions, organic particles, suspended particles, microorganisms, and gas. Purification methods may differ, depending on the end use of the water, volume, or the difference between initial water quality and the quality desired after treatment.

Various technologies can be used to produce Type 2 water; however, the combination of reverse osmosis (RO) and electrode ionization (EDI) appears to be the most efficient way of obtaining consistent high-quality pure water, both in terms of resistivity and low levels of total organic carbon (TOC). This is due to the ability of the combined RO-EDI purification technologies to remove a large spectrum of contaminants, including ions, particulates, and organic compounds. Merck Millipore was one of the first companies to use EDI technology for the production of pure laboratory water.

In the Elix® module, ion-exchange resins are continuously regenerated by an electric current. This procedure needs only a low quantity of energy, and requires no special maintenance or chemical regeneration that would deteriorate the resin bed. This unique process, patented by Merck Millipore, has become the new standard for the production of Type 2 water, and is replacing conventional distillation and de ionization units in the laboratory.

Elix® technology vs. distillation
One of the important objectives that Merck Millipore is striving to achieve is long-term environmental sustainability and a substantial reduction in the consumption of non-renewable raw materials such as energy and water. Consequently, to measure the differences between an Elix® 3 system* (Figure 1) and a traditional distillation system, energy and water consumption, as well as global warming potential (GWP) for the two systems were analyzed.

Scope of the study
A production of 20 L of pure water per day was considered for both purification systems, over a daily production period of 6.7 hours.

This is the standard level of production and use for an average laboratory. Utilization of the systems was considered for 20 days per month and 12 months per year.

Elix® systems use a combination of purification technologies, including pretreatment, patented Elix® electrode ionization technology, and UV light sanitizing, to produce pure water of constant quality suitable for use in analyses at parts per million (ppm) or parts per billion (ppb) levels.** The Elix® 3 water purification system considered for the study uses 15 litres of water to produce three litres of pure water per hour, and consumes 0.160 kWh of energy to produce one litre of water (0.045 kWh when in stand-by mode).

On the other hand, the traditional distillation system requires 26.6 litres of water to produce the same quantity of pure water, while consuming 1.65 kWh of energy.

Operating the Elix® 3 system for a period of one year requires two Progard® S2 purification cartridges. The production/distribution for each of these consumables requires consumption of 39.6 kWh of energy and 107.8 litres of water. 5.9 kg of equivalent CO2 is generated for each cartridge.

Results & conclusions
When all of the above data are considered, operation of the two systems requires overall annual water consumption of 24,270 litres for the Elix® system, as compared to 44,880 liters for the distillation system (Figure 3). This results in savings of nearly 50 per cent for the Merck Millipore system.

With regard to annual energy consumption, savings are even greater, with 617 kWh calculated for the Elix® 3 system versus 2,614 kWh for the still. In terms of annual global warming potential***, the Elix® 3 system (including consumables) produces 199 kg of CO2 versus 944 kg for the distillation system.

In conclusion, for the one-year period considered, the Elix® 3 purification system proves to be significantly more sustainable than a still. All three parameters taken into account by the study — energy consumption, water consumption and global warming potential — were much lower for the Elix® system. Low running costs, constant operation and minimum maintenance thus make the RO-EDI purification method superior to distillation for laboratory activities.