This article looks at the use of ion exchange water softeners. It explains what they are, how they work to combat the effects of hard water, and how the effectiveness of the ion exchange process can be maintained to ensure softened water remains on tap.
Using water softeners in hard water areas
If you live or work in a hard water area, you will be all too familiar with the issues caused by scale forming in your kettle, washing machine or iron. Over time, the build-up of scale can cause significant damage and stop the appliances from working altogether.
Industrial and commercial equipment experience just the same problems with hard water, and not just on kettles either. Minerals suspended in water can cause huge damage to plant and machinery, so it’s perhaps not surprising that many companies invest in water softening technology to try to deal with their hard water problems.
Domestic water softeners often work by filtering the tap water through a cartridge, designed to filter out the problematic minerals. However, in an industrial setting, other technologies are more appropriate, including ion exchange water softening.
How do ion exchange water softeners work?
Just as with other forms of water softening, ion exchange softeners take the minerals which cause limescale out of the hard water before use. But what differs is the way in which this is done, which is radically different from the more conventional techniques used in domestic settings.
Ion exchange is a chemical process, which involves a reaction which swaps the “hard” minerals in water, mostly magnesium and calcium, for other “softer” minerals, mostly sodium. This is possible because of the chemical make-up of the minerals concerned. They are ionic, which means they have an electrical charge in the atoms which make up the chemicals. An ion exchange process happens because of basic physics; like charges repel, and opposite charges attract.
A water softener which works using the ion exchange process takes the calcium and magnesium – the “hardness” minerals – which are dissolved in water, and exchanges them for sodium. The sodium comes from the resin beads used in the ion exchange softener, and are added into the water system, and the hard minerals are filtered out through the base of the system.
The practicalities of the ion exchange process
In an ion exchange system, the hard water flows into the system and then passes over man-made ion exchange resin beads. These are usually held in a pressure vessel tank. The most commonly used resin for modern ion exchange softeners is called polystyrene divinyl benzene. These are in the form of millions of little plastic beads, which contain negatively charged ions. The ions in the hard water which we are interested in – sodium, calcium and magnesium – all carry a positive charge.
Before the ion exchange process starts, the resin beads contain sodium ions, which have a positive charge. As the hard water containing magnesium and calcium ions flows into the softener system, these ions are attracted towards the resin bed, displacing the sodium ions.
Next steps in the water softening process
There are a couple of things which might happen next in the ion exchange process, depending on the composition of the source water. Often, the ions in water don’t always have the same strength of charge. The resin bed might then prefer the strongly charged magnesium and calcium ions, in contrast to the sodium ions which might have a weaker charge.
Minerals which are displaced through the ion exchange process pass through the layer of resin in the tank, and then out of the water softener outlet, allowing the “soft” water to flow out into the system.
How to regenerate ion exchange softener resin
Eventually, there were will be no sodium ions left in the bed to be displaced by calcium or magnesium. At this stage, the resin is “exhausted” and won’t work any more unless it is regenerated. The most common method of resin regeneration is by using a solution of brine.
Water softener systems will incorporate a brine tank, which has a reservoir to mix water with salt. As the brine comes into contact with the resin, the sodium ions from the salty water will displace the magnesium or calcium ions which have been stored in the resin bed from the previous process. Even though the salty sodium ions may be weaker, their sheer quantity means they have the power to push the magnesium and calcium out of place. Although this process may take some time, eventually all of the magnesium and calcium in the resin bed will have been replaced by sodium. At this point, the resin bed is considered recharged or regenerated, and ready to treat another batch of hard water.
Expert solutions for hard water areas
Water Treatment Services offer a comprehensive range of expert solutions for the management of hard water, protecting plant and machinery from the detrimental effects of limescale.
Find out how we can help trouble-shoot problems, improve the thermal performance of your water systems, lower energy bills, reduce maintenance costs and down-time, and extend plant life-cycles.
Our industrial water treatment experts can provide advice and full support to help you identify the most appropriate strategies for managing your water systems. We also provide specialist analysis, trouble-shooting, expert witness and litigation support on issues associated with water systems.
With offices in London serving the South and South East England, Manchester (North West), Birmingham (Midlands), Bristol (South East England and Wales), Leeds (North and North East) and Glasgow (Scotland), supported by regional teams of specially trained engineers, water treatment specialists and technicians we offer cost effective environmental support solutions across the whole of the UK and Ireland.
Contact us today to learn how our water softener solutions can help improve the performance of your water systems.
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