The scale of the problem

Published:  23 September, 2014

Many UK water systems struggle with the build up of scale. Traditionally, salt-based systems have been used but, given the many concerns about this option, Tony Klimas suggests the industry consider an alternative solution

Across Europe, approximately 300,000 tonnes of salt are used each year to soften hard water; 22,000 of which are used in the UK. That’s not to mention the one million cubic metres of water used every day in the whole process. Salt-based treatments are still the accepted norm for softening water, despite alternative technologies emerging over the past several years to combat the many issues that arise from scale build up.

In boilers and heating systems, scale prevents integral parts from functioning correctly and also acts as an insulator, which means heating systems need to fire up for longer in order to transfer the required amount of heat. This then has a domino effect of increasing the energy used, and the end cost of heating the building. The problem is so significant that Part L of the Building Regulations requires the pipes and water circuit of combination boilers to be treated in areas where water hardness is higher than 200 parts per million (ppm). With over 60% of England and Wales designated a hard water area – that regulation applies to hundreds of thousands of households.

Salt-based softeners

Scale comprises calcium, magnesium and bicarbonate. Deposits, once formed, are very hard to break down –impacting the flow of water through pipes and forming crusts on heat exchangers and moving parts such as valves. A salt-based water softener works through ion-exchange; the calcium and magnesium particles are replaced with sodium particles. The calcium and magnesium particles then attach to polymeric beads which are stored inside the softening chamber. Essentially, the particles switch places. The harder the water, the more sodium is exchanged.

However, this process has a finite shelf life with softeners needing to be replaced every five to 10 years depending on the hardness of the water and the size of the system. In addition to this cost, from a health perspective there have been concerns that the sodium-heavy water created by softeners is not particularly healthy to drink, especially for those on a low sodium diet or who are hypertensive. There may also be an increase in the number of metal ions in the water, such as copper and lead that have leached out during the exchange process.

The most widely known issue surrounding salt-based water softeners, however, is their environmental impact. All of the sodium ions exchanged are discharged into the sewage system, making the waste water highly concentrated. Even after the waste water has been treated – an expensive process in itself – the water may still have higher than average salt content, rendering it unusable for irrigation, for example. The concern is so great the WateReuse Foundation recently completed a scientific evaluation of alternative technologies with the aim of finding a solution that works for multiple sectors.

Finding an alternative

One of the methods included in the research was template assisted crystallisation (TAC), which works by forming microscopic crystals in the water to prevent calcium, magnesium and bicarbonate ions from coming together, thereby preventing scale from building up. The WateReuse study acknowledges the relative newness in using TAC to combat water hardness. One of the comments in the subsequent report is the need for greater education in the market about how the technology works and its benefits over the more typical water treatments, like salt, ion exchange, magnetic cleaners or electrically induced precipitation.

Indeed, the results from the study suggest that TAC can outperform all the above listed technologies, creating an even stronger case for greater awareness and use of the system across hard water areas in the UK. In all of the test rigs – all set up and carried out to the German standard protocol DVGW Article ‘W512’ – Verification of Water Treatment Device for the Reduction of Scale Formation – NEXT Filtration’s ScaleStop system, which uses TAC, reduced scale by a minimum of 88% and often much higher. When ScaleStop was compared with the results of other systems the difference is even more significant. For example, the electromagnetic system and the electrically induced precipitation device only reduced scale by 50% and left considerable soft scale in the water, while in the same testing set-up the quantity of scale in the TAC-treated water was not significant enough to assess.

The study also looked at the cost of implementing a TAC system based on a 10-year life cycle. Including capital costs, the ScaleStop system fell well below the costs of electrically induced precipitation, ion exchange and capacitive deionisation.

Reducing the volume of salt being washed into our sewage systems and overall water consumption are two compelling environmental goals and, based on the scientific research completed by WateReuse, the effectiveness and overall costs of TAC make it a viable alternative to reduce scale across the UK. Over the next few years, it’s likely we will see a marked increase in the use of this technology over the current options, as we seek to protect and extend the life of our heating and water systems.

Tony Klimas is sales manager at Next Filtration