Key points
One element of water treatment that can be overlooked, to a greater or lesser degree, is the use of water softeners to overcome issues, some very significant in industrial processes, arising from the use of hard water.
Commonly, scale arising from hard water reduces pipework diameters, damages equipment, and can leave residues on products, while contributing to inefficiencies in heating and cooling processes. Water softener systems can provide simple, low-cost answers, but at a cost going forwards.
By exchanging scale-forming ions, such as calcium and magnesium, with highly soluble sodium, users have an immediate resolution to the problem. But this solution is not without its own challenges.
The initial benefits of traditional water softeners can be negated through inefficiencies leading to high running costs and a subsequent reduction in their overall value. It’s not all negative news and views, however, for water softeners.
The emergence of “next-generation” technologies provide more efficient and cost-effective methods to prevent scale while limiting the cost of salt and water for regeneration processes, and using less energy in doing so.
Swapping ions for softened water
The quantity of magnesium, calcium and other dissolved minerals determines water hardness. That is well recognised, of course; but less well known are problems that can arise on a wide scale by even low levels of the minerals, which, for example, at just 8mg of calcium carbonate per litre can produce scale-forming ions, when water is boiled, resulting in the inhibition of heat transfer and therefore reduced efficiency.
Water hardness is a problem throughout much of Europe. Using the UK as an illustration, we see that potable water in most of the east, south and central areas of England contain more than 200mg of calcium carbonate per litre.
Calcium and magnesium ions are only sparingly soluble, easily coming out of solution and forming a solid layer of scale. This is a particular problem when water is heated, as in industrial processes, because scale can build up very quickly, raising costs and reducing efficiencies.
The most common way to soften water is to replace calcium and magnesium ions with more soluble sodium, using ion exchange resins. Sodium stays in solution, even when heated and this reduces scale build-up. Once the resins are exhausted, they are washed with a brine solution, removing the calcium and magnesium ions, and exchanging them with sodium.
High running costs
With ion exchange being a well-established, traditional approach to treatment, many businesses already incorporate it in their operations. Although the cost benefit in reducing minerals in water is clear, ion exchange-based water softener systems often carry high running costs, requiring large volumes of salt – and water – for the regeneration processes.
But other costs are involved, resulting from running regeneration cycles for too long and not investing in automation and monitoring of effluent flows. Typically, cycles often work on a timer basis, meaning that in periods of lower flow users can create excess waste streams completely unnecessarily and at a cost.
Guesswork can be taken out of regeneration cycles through the use of advanced conductivity sensors in new water softener systems. The sensors detect the moment that ion exchange resins are regenerated -with mineral ions – and stop the rinsing cycles.
The resins work by being charged with sodium ions and then introduced to the (hard) water, resulting in the removal of calcium. Over time, the resin beads that facilitate this exchange become saturated with hardness minerals and need to be regenerated.
Water softeners: Less salt, less effluent water
When combined with a counter-current regeneration flow, the new systems use up to 60% less salt, and generate up to 80% less effluent water, than traditional systems.
Counter-current regeneration works by percolating the ion exchange resins opposite to the flow of the water during the softening process, instead of percolating the brine in the service direction, as is the case with co-current regeneration.
Counter-current regeneration results in the best quality salt solution being used on the final beads in the media bed to improve water quality and capacity during service.
Such new systems come of Envirogen’s “EcoSave” technology, which, in addition to its counter-current regeneration flow capabilities, utilises additional water hardness monitoring to adjust dosing according to water hardness changes. The result is the further improvements in efficiency.
Corporate social responsibility
Corporate social responsibility (CSR) has a role to play in water treatment. With that in mind, organisations can take the steps necessary to minimise the volumes of salt and water and energy uses and help ensure that any water returned to its source/drains after use is as unpolluted as possible, even potable.
Reducing water usage makes sound financial, environmental, and social sense; social in the case of low water levels and droughts affecting the general population, business, and local authorities.
Reducing the quantity of salt used with next-generation water softeners results in fewer salt deliveries, meaning a reduction in the number of large goods vehicles on the roads and fewer emissions. Direct costs savings are the clear result.
With less time and resources devoted to managing salt supplies, there is a notable decrease in interruptions to business operations caused by delivery schedules, thereby streamlining the overall management process.
Water conserving model
Water can be reclaimed for recycling, and re-used time and again, where water re-use technologies are incorporated into a full treatment system, optimising that approach with regular servicing and maintenance of equipment.
A water-resilient business model can involve multiple steps, some of them very simple. The steps can include (i) identifying opportunities for re-use and recycling (ii)analysing data, to answer the question “'What volume and quality of water is being sent to drain or elsewhere?” (iii) agreeing which processes can use reclaimed water and identifying their location on-site (iv) implementing a pilot project founded on these steps, and (v) basing a solution on lessons learned and knowledge gained from the pilot project.
Additionally, insights can be gained by listening to those who have already implemented water saving practices and speaking with external water treatment experts.
Further benefits accrue from deploying the most appropriate water softener system for the application, with future proofing potential built in. For example, where space is an issue, and/or likely future-proofing potential required, modular skid designs provide a very suitable answer.
A modular solution based on a two vessel (duplex) design can supply up to 50m³/hr of softened water with less than one part per million (ppm) total hardness, with lower maximum flow rates also catered for. Triplex configurations can be deployed for higher flow rates.
Where a water saving model is implemented, a modular unit is additionally useful through its ability to be embedded within a total water treatment and process filtration solution.
To conclude, understanding the true cost of using water softeners can be addressed by looking at the bigger picture, encompassing not only the latest technologies for cost reduction and improved efficiencies but also the sound environmental and social elements that have positive implications for the business, its costs and beyond.
