Making pure water green

Water purification in the lab is a vital requirement – but what environmental impact does your system have?

The water purification system is an essential part of your laboratory. Many analytical and bioscience applications now demand ultrapure water at the turn of a tap and, as a result, the modern laboratory water purification system uses a combination of state-of-the-art process technologies such as ion exchange, reverse osmosis and UV photo-oxidation. But how much thought have you given to the environmental impact of your system and how it might be improved? Perhaps now is the time to consider just how green your water purification system is.

We are all aware that a key measurement of environmental impact is carbon footprint. It quantifies the amount of greenhouse gases, in kg of carbon dioxide equivalent that a piece of equipment like a water purification system produces in the whole of its life from manufacture to final disposal. It includes the “embedded carbon” in the product that is, for example, the plastic content, heating, chemical use, transportation and packaging during the initial manufacturing and supply. It also includes the “operational carbon” which arises from the power, chemicals and consumables used in operation throughout the product’s life. It even includes the carbon released by the technician’s car when he visits for routine servicing. Your supplier should be able to help you with this calculation and indicate where improvements can be made. It is certainly something you should consider carefully when buying a new water purification system so that you can select the most sustainable system for the laboratory’s requirements and environmental goals.

The most widely used treatment technologies in laboratory water purification systems are adsorption; ion exchange; reverse osmosis; micro- and ultra-filtration and ultraviolet irradiation. The various steps are usually provided in the form of cartridges which simply plug in to the system and are replaced when they become ineffective. Most of these have a high embedded carbon content. Adsorbents range from synthetic oil based polymers to activated carbon, which may be manufactured from coal or from renewable sources like coconut shell, whilst ion exchange resins are synthetic polymers. The high performance membranes used in water purification systems are mostly manufactured from oil-derived polymers like PES and PVDF, and similar materials are used for manufacturing microfiltration and ultrafiltration membranes.

The cartridges that contain the “active materials” are also plastic. Because the quality of the water produced by laboratory purification system is so high – contaminants are measured at ng/l levels – it is vital that the materials do not release any leachable substances. For this reason polymers like polypropylene, perfluoroalkoxy (PFA) and PVDF are commonly used.

The relatively high embedded carbon content of the cartridges means that they are likely to make a significant contribution to the overall footprint. It will not be possible to eliminate these consumables, but it may be possible to extend the period between replacements. This can be achieved via one of the pre-treatment solutions available such as the well established service deioniser (SDI). This approach uses regenerable ion exchange cylinders installed ahead of the laboratory water purification system which reduces the load on the laboratory unit making its ion exchange cartridges last longer, saving money and reducing waste. When the cylinders are exhausted they are returned to your supplier’s media conditioning centre for regeneration. Check that this is fully ISO14001 compliant, that it minimises energy consumption and chemical use and also has a sustainable waste disposal programme.

Driving the water purification system’s pump and controls needs electricity, but it should only run when required. Does your system have the latest energy saving technologies such as variable speed pumps and “sleep mode” operation for periods of no demand? These can significantly reduce energy costs as well as carbon emissions.

A goal of product development is to minimise the use of conventional cartridge consumables by using alternative, sustainable technologies, such as electrodeionisation (EDI) which eliminates the need to replace consumables deioniser cartridges.  This technology is already established for use in laboratory water purification systems, and has proven to be effective for higher volume requirements.

Most water purification systems have a plastic cabinet. This may, at first sight, appear carbon intensive but its durability, corrosion resistance and light weight means that it’s often the best choice. But is that plastic recyclable?

The electronic “brain” that controls the purifier and monitors water quality should be fully compliant with the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment (RoHS) Regulations 2008 which ban a variety of toxic materials. But does your supplier comply with the Waste Electrical and Electronic Equipment (WEEE) Directive and offer as part of their service the removal and recycling of your equipment at the end of its life?

Most water purification consumables are simply disposed of along with other waste from the laboratory and that often means landfill.  However, it is possible to recycle these consumables. Some companies have adopted the “Eco-Box” approach: a simple, safe and sustainable solution for the collection and disposal of lab water consumables. Your used ion exchange cartridges, deposited in the Eco-Box, can be recycled and the resins re-used in SDI cylinders. Similarly membrane cartridges can be dismantled and the plastics separated and recycled as appropriate. Activated carbon can be batched and regenerated thermally for reuse. UV lamps that contain mercury can also be safely disposed of via the Eco-Box.

Water is a precious and rapidly diminishing resource. Water reuse and recycling is practised in many industrial applications but there is no reason why this should not be extended to laboratories. Most of the waste water from your laboratory water purification system is water which, for one reason or another, does not meet specification but is nevertheless of a good enough quality to be used elsewhere. Whilst this may be a relatively small flow it is worthwhile looking for an opportunity for re-use such as glass washing, make-up to a cooling circuit or simply for recycling to the raw water tank.

So if you can answer yes to all these recycle options, then you can congratulate yourself that your water purification system is pretty green. You may argue that the carbon footprint of a laboratory is likely to be relatively small by comparison with that of a factory, but any reduction in carbon footprint that can be achieved by improving the water purification system is significant. In the words of the supermarket advert: “every little helps”.