About of Lime softening

Lime softening is the process of adding lime to hard water to soften it.It has several advantages over ion exchange methods,but is primarily suitable for commercial processing applications.

Chelating agents

Chelating agents are used in chemical analysis,as water softeners, and are ingredients in many commercial products such as shampoos and food preservatives.Citric acid is used to soften water in soaps,personal care products and laundry detergents.A commonly used synthetic chelating agent is ethylenediaminetetraacetic acid (EDTA), which is available as the tetrasodium or disodium salt.Alternatives such as sodium phytate/phytic acid, tetrasodium glutamate diacetate,and trisodium ethylenediamine disuccinate are increasingly being used due to environmental and aquatic toxicity concerns over the widespread use of EDTA in household and personal care products more common.

Washing soda method 

In this method, water is treated with a calculated amount of washing soda (Na2CO3) to convert calcium and magnesium chlorides and sulfates to their respective carbonates, which precipitate.

CaCl₂ + Na₂CO₃ --> CaCO₃ + 2NaCl
MgSO₄ + Na₂CO₃ --> MgCO₃ + Na₂SO₄

Distillation and rain water

Since Ca2+ and Mg2+ exist as non-volatile salts, they can be removed by distilled water.Distillation is prohibitively expensive in most cases. Rainwater is soft because it distills naturally during the water cycle of evaporation, condensation and precipitation

Reverse osmosis

Reverse osmosis uses a pressure gradient applied across a semipermeable membrane to overcome osmotic pressure and remove water molecules from solution with hard ions.The pores of the membrane are large enough to allow water molecules to pass through; hardness ions such as Ca2+ and Mg2+ cannot pass through the pores.The resulting soft water supply is free of hard ions and does not require the addition of any other ions.A membrane is a water filter that requires regular cleaning or replacement maintenance.

Non-chemical devices

Some manufacturers claim that the electronics they produce can affect how minerals interact with water so that the minerals don't stick to surfaces.Since these systems do not work through ion exchange like traditional water softeners, one benefit users claim is that no salt needs to be added to the system.This system does not remove minerals from the water. Instead, they only alter the downstream effects that mineralized water would otherwise have.These systems do not fall under the term "water softening" but rather "water conditioning".Similar claims for magnetic water treatment are not considered valid.For example,when this magnet setup was scientifically tested, no reduction in fouling was found.

Alternatives to ion-exchange water softeners

Removing or replacing minerals in hard water is called water softening. Another type of water treatment is called water conditioning, in which minerals remain in the water, but are changed so they don't form scale.Although the United States has standards for measuring minerals in water, there is no standard for measuring the scaling ability of water.Instead, the researchers used the German DVGW-W512 protocol.Rainwater contains dissolved carbon dioxide from the atmosphere.Some of the dissolved carbon dioxide reacts with water to form carbonic acid, which remains in solution. Minerals containing calcium and magnesium form soluble bicarbonates when exposed to carbonic acid.Water that contains these minerals is called "hard water."When hard water in a plumbing system is heated, carbon dioxide goes out of solution and bicarbonate becomes carbonate, which is much less soluble.The carbonates bind to the pipe surface, seeding further crystal growth, forming hard scale.Physical water treatment (PWT) devices cause microscopic mineral crystals to form and remain in suspension as they flow with the water, while also acting as seeds for further crystal growth.When the water is heated, the minerals crystallize on these seeds rather than the plumbing. Dissolved minerals become suspended insoluble solid particles that pass through the system without binding to pipe surfaces.