Water Quality - Softening and Sustainability Issues

Water quality is often overlooked when thinking about water sustainability, but the quality of treated water has a large impact both at the building scale and at the ecosystem scale.  Water softening, which is usually the method for mitigating hard water sources, is not just an issue for building users, but has a large impact on energy use and water quality at a community or regional level.  Some areas with a very hard water supply find that salt-based water softening systems contribute to salinity of natural water bodies, which not only alters water ecosystems, but has impacts for reuse of water in agriculture or municipal water supplies.  For example, irrigating with high salinity water can reduce crop yields, which can be even more problematic as agricultural fertilizer runoff can also contribute to water salinity.  Further, some communities where conventional salt-based systems are very popular have found that municipal water treatment plants have experienced increased costs from having to mitigate higher salinity water.  

An alternative to the conventional salt-based water treatment systems is a physical water treatment system (PWT), which conditions water to avoid scale buildup.  Instead of a chemical change that occurs when magnesium and calcium ions are exchanged with sodium ions in the conventional softening system, PWT systems change the physical characteristic of water.  Template assisted crystallization (TAC) is an example a PWT system.  In this system a coated template re-arranges water ions in such a way that catalyzes the calcium, magnesium, and bicarbonate ions coming together.  Instead of having these ions eventually form scale on the pipes from water systems downstream, they will rapidly form a soft scale and remain suspended in the water.  These soft scales get flushed out of the system and will return back into dissolved particulates, essentially returning the water to a similar state as before it went into the conditioning system.  

 

The benefits of the TAC method for conditioning hard water include:

  • Reduces scale buildup that can damage or reduce performance of building water systems;
  • Reduces redundant water use from traditional salt-based water softening systems;
  • Reduces the impact from high salinity (salt and other substances) discharge water from traditional water softening systems;
  • Indirectly reduces energy by preventing scale buildup in water heating systems;
  • Smaller tanks for mechanical room design and access;
  • Reduces operational costs.

The impact of converting from a salt-based water softening system to a PWT conditioning system will depend on what water systems you use in your building as well as your water sources.  Some areas may have varying levels of hardness, which is measured by grains or mass of particulates in a single gallon of water, and may or may not need water softening or conditioning.  There are also particular geographies that have high levels of hard water. To learn more about water hardness and geographic patterns of hard water, visit the USGS Water-Quality Information site.  

The water systems utilized in a building will also make a difference in impact.  Buildings that utilize water heating systems, such as a hot water heaters, boilers, or humidifiers, with hard water will also get a lot of benefit from a highly effective water softening system.  In particular, existing building retrofits and historic structures that may have existing piping are also susceptible to problems with water scale.  In these applications, water systems are particularly impacted by scale buildup, which can reduce output, increase operational energy, and reduce the life of the equipment as well as increase the operating and maintenance costs.

A carefully specified and designed water system can help reduce environmental impacts as well as reduce the cost of maintenance for water systems in buildings.  This one example of template assisted crystallization water conditioning is one of many ways that water is extremely important to sustainability.  It is not always about reducing water use, but about water quality, and even impacts energy-use.   To read more about TAC and other PWT conditioning see HPAC Engineering’s article from 2010 and GreenSource’s article from 2011.