Water Softening & the Environment
About 60% of the UK has a water supply that is ‘hard’. This means it contains relatively high levels of calcium and magnesium in the form of carbonates, resulting from rainwater leaching through limestone rock.
The most effective way to overcome the effects of hard water is to soften using an ion exchange water softener.
Whilst the use of ion exchange water softening systems does have an environmental impact, this is more than outweighed by the benefits in energy savings and reduced consumption of detergents and other chemicals.
Whilst not a comprehensive list, some of the substantiated benefits of using softened water are listed below:
Work published in France shows that a 1mm increase in scale thickness can reduce heating efficiency by an average of 6%, with the first 0.4mm showing a rate as high as 10%.
Another study by New Mexico State University, showed that over 29% more energy was used by gas heaters run on hard water, and 21% more with electric heaters.
Detergent & Cleaning Agent Consumption
The Association Français pour l’Etude des Eaux found soap and detergent use more than doubled in hard water. Since then detergent formulations have been adapted to take into account hard water, by the use of additives such as phosphates, yet many brands still indicate considerably different usage rates for hard and soft water.
Both the additional detergent and the ‘softening’ additives increase the environmental burden of laundry and bathing activities.
Because of its scaling effects on sanitary ware, anti-scalants are often necessary in hard water areas. These tend to be acid based, so are both costly and have an environmental impact.
A study carried out in a Chicago YMCA laundry, found that softening the water supply increased the life of frequently washed household items such as sheets, pillow slips and bath towels by 20-40%.
Life Cycle Analysis (LCA)
As yet, analyses of the full life cycle of water-based processes are very limited. However, a Swiss study on domestic clothes washing showed that ion exchange softening was environmentally better than either the use of unsoftened water, or captured rainwater.
Environmental Impact of Softening
Raw material consumption
Softening equipment is manufactured from various materials, including common metals and plastics, which are recyclable. It should also be noted that the equipment has a long life, typically over 15 years, and requires minimal maintenance.
Salt (sodium chloride) is the only consumable product used in the process. Salt is abundant in nature, in both geological deposits and the sea. It is relatively easy to extract and process, with little chemical use or impact on the landscape. The principal environmental impact is the energy used in evaporation, which can be minimised by the use of efficient evaporator systems.
The regeneration cycle of the softening process discharges a quantity of sodium chloride into the drainage system, and sodium ions are added to the softened water.
Studies on septic tanks and sewage systems have repeatedly shown that the sodium/salt burden has no harmful effect. Sodium does not bio-accumulate which ensures that there are no long term environmental effects.
Modern equipment is designed to have a high salt efficiency, so effects on the overall chloride and sodium environmental burden is minimised.
The regeneration and backwash cycles of the softener do use more water than standard consumption. However, modern demand-driven equipment keeps wastage to a minimum.
Soft Water & Metal Corrosion
Because naturally soft water has been associated with increased corrosion in water supply systems, there has been concern that softened water might have a negative impact on metal.
However, tests carried out by the US Environmental Protection Agency have clearly demonstrated that there is no significant difference in corrosion performance between softened water and its source water. Indeed there were indications that in some cases softened water may be less corrosive.
Le Grand Livre de l’Eau
M A Bernardis, La Manufacture 1990
Softened Water Energy Savings Study – Controlled Experimental Testing Program on Household Water Heaters
Engineering Experiment Station, New Mexico State University, Las Cruces, New Mexico, 1979
La Dureté de l’Eau Intérêt Économique de l‘Adoucissement Collectif Pour l‘Usager.
Etude de synthèse de l’agence de l’eau Artois-Picardie
Association français pour l’étude des eaux 1981
Benefits of Using Soft vs Hard Water in Laundering Operations
R W Peters, C M Ladisch, Research report sponsored by Water Quality Association (USA) October 1990
Life Cycle Assessment of Rainwater Use for Domestic Needs
V Bronchi, O Jolliet & P Crettaz
Ecole Polytechnique Federale de Lausanne, Institute of soil and water management. Paper given at 2nd Inter-Regional Conference on Environment-Water 1999
Ion Exchange Softening: Effects on Metal Concentrations.
TJ Sorg, MR Schock, and DA Lytle. Water Supply and Water Resources Division, National Risk Management Research Laboratory, Office of Research and Development, USEPA, Cincinnati, Ohio.
Journal AWWA, 91(8):85-97 1999
The Effect of sodium discharge from water softeners into the septic fields of New Jersey
JCF Tedrow, Rutgers University 1997
Potential Effects of Water Softener Use on Septic Tanks Soil Absorption On-site Waste Water Systems
Corey, Tyler and Holotoo University of Wisconsin- Madison