There are two types of industrial water softening and municipal water softening ion exchange options, cation and anion softening. The basic difference is that cation exchange materials only react with positively charged ions when softening water, while ion exchange materials only react with negatively charged ions while softening. Cation ion exchange water softening works by swapping out hard water ions like calcium, magnesium, manganese and iron for sodium.

Lime softening of industrial or municipal water involves mixing lime-soda with water, allowing the resulting sludge to settle, and then drawing off the clear, softened water. Optimal results can be achieved by using hot water.

Advantages of Each Type of Water Softening
• Each water softening technique carries its own set of benefits. For ion exchange, they range from lower capital and operational costs, ease of use and minimal staff requirements to safer handling (salt is the only additive in this method).
• For lime softening, benefits include additional water treatment beyond hardness (suspended matter is also removed, and alkalinity and silica are reduced). Operational costs can be lower if the volume of water is high.

Disadvantages of Each Type of Water Softening
• Ion exchange will only remove ions that create hard water, so if there are other unwanted materials that need to be removed, another process will need to be applied. In some locations, brine from the exchange process can be difficult to properly dispose of.
• Lime-soda softening does not remove all hardness from water, it only reduces the amount. This method also requires full-time, specially trained staff to run equipment, which adds quite a bit to operational costs for industrial and municipal water systems. Material handling carries some risk since the chemicals needed are harmful compared to than salt.

The Bottom Line
There are a few deciding factors for making a decision on the right direction for your industrial or municipal water softening system:

• The first is how much water will need to be treated per day? For most applications, ion exchange is going to have the lowest initial capital investment and the lowest operating costs. However, for large applications, lime soda softening can be more cost effective.
• A second consideration for water softening is what specifically needs to be addressed (just hardness, or other particulate matter as well?).
• The last consideration is staff capabilities. Do you have enough staff to dedicate to running a lime softening plant?

More information on the process, benefits and disadvantages of both can be seen here.

To find out what size of ion exchange softener you would need, click on our FREE water softener calculator and sizing tool.