Lime-Soda Ash Water Treatment Method

In previous articles, we have already explained some common water treatment methods. Here, the lime-soda ash treatment is commonly used by industry for reducing hardness of water.

Lime-soda ash treatment for the reduction of hardness involves the addition of slaked lime [Ca(OH)2] to a hard water supply to remove the carbonate hardness by precipitation with the precipitation being removed by filtration. Non-carbonate hardness is in turn reduced by the addition of soda ash (Na2C03) to form an insoluble precipitate which is also removed by filtration.

soda ash

This particular method of removing hardness sometimes used by municipal water plants to reduce the amount of calcium and magnesium in a water supply. While it is quite effective in reducing hardness, it is not a complete removal treatment.

Often when a city has a raw water source that has 35 to 40-grain hard water, the local water system will use the lime-soda ash treatment to reduce hardness to between 5 and 10 grains.

Lime-soda ash treatment is especially effective if a water contains bicarbonate (temporary) hardness. Where calcium and magnesium are primarily in chloride or sulfite compounds, this treatment is noticeably less effective.

Slaked lime is used to remove calcium bicarbonate from water. In the water to be treated, the slaked lime ions react with the calcium bicarbonate to form the very slightly soluble calcium carbonate. This precipitated material is usually removed by first settling and then filtering.

Ca(OH) 2+ Ca(HC03)2 --> 2 CaCO3 + 2 H2O

Calcium hydroxide plus calcium bicarbonate reacts to form calcium carbonate plus water

NOTE: The arrow pointing down (¥) indicates the formation of an insoluble compound.

Many cities across the U.S. have started to ban traditional water softeners from their communities even though they have hard water. These ion-exchange systems use large amounts of salt, which is then flushed down the drain and harms the environment. Sanitary departments are then forced to build treatment plants to remove the salt and they, in turn, pass these costs down to the consumer through higher monthly water bills. Thus many cities have decided that it is not worth the cost and effort and have banned the use of salt-based water softeners altogether.

Salt-free water softeners are a better solution. These systems use catalytic conversion to safely soften water without the use of salts and are much better for our environment and local waterways. Salt-free water softeners deliver all the benefits of traditional water softeners and are approved for use by every community.


Water Softeners
No Salt, No Mess, No Scale - No Problem.

According to recent news and reports, most tap and well water in the U.S. are not safe for drinking due to heavy industrial and environmental pollution. Toxic bacteria, chemicals, and heavy metals routinely penetrate and pollute our natural water sources making people sick while exposing them to long-term health consequences such as liver damage, cancer, and other serious conditions. We have reached the point where all sources of our drinking water, including municipal water systems, wells, lakes, rivers, and even glaciers, contain some level of contamination. Even some brands of bottled water have been found to contain high levels of contaminants in addition to plastics chemicals leaching from the bottle.

A good water filtration system installed in your home is the only way to proactively monitor and ensure the quality and safety of your drinking water. Reverse osmosis water purification systems can remove 90-99% of all contaminants from the city and well water to deliver healthy drinking water for you and your family.

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To remove the magnesium, additional lime is used. The reaction for this process is:

Ca(OH) 2 + Mg --> Mg(OH) 2 ¥ + Ca++

Calcium hydroxide plus magnesium ions react to form magnesium hydroxide plus calcium ions

This step has simply replaced the magnesium with calcium. If soda ash is then fed into the water, the calcium will precipitate as calcium carbonate:

Ca++ + Na2CO3 --> CaCO3 ¥ + Na+

Calcium ions plus sodium carbonate react to form calcium carbonate plus sodium ions

There are many variants possible under this general heading. Their discussion here, however, is not essential to our course of study.

Lime-soda ash treatment becomes increasingly costly when the hardness of the water must be reduced to less than 5 grains. Municipally, the complete elimination of hardness is rarely attempted as less than 5% of a municipality's water is used for home consumption. The use of soda ash for the reduction of non-carbonate hardness increases the sodium in the effluent water in the same proportion as ion exchange softening.

The use of the lime-soda ash treatment is impractical for individual home softening of supplies. For one thing, there are difficulties in feeding lime and soda ash into raw water. Further, close control of the operation is required both while the settling and filtering occur.

An additional deterrent to home use of the lime-soda ash treatment is the size of the equipment necessary, together with the high cost of this method of treatment.

Many cities across the U.S. have started to ban traditional water softeners from their communities even though they have hard water. These ion-exchange systems use large amounts of salt, which is then flushed down the drain and harms the environment. Sanitary departments are then forced to build treatment plants to remove the salt and they, in turn, pass these costs down to the consumer through higher monthly water bills. Thus many cities have decided that it is not worth the cost and effort and have banned the use of salt-based water softeners altogether.

Salt-free water softeners are a better solution. These systems use catalytic conversion to safely soften water without the use of salts and are much better for our environment and local waterways. Salt-free water softeners deliver all the benefits of traditional water softeners and are approved for use by every community.


Water Softeners
No Salt, No Mess, No Scale - No Problem.

According to recent news and reports, most tap and well water in the U.S. are not safe for drinking due to heavy industrial and environmental pollution. Toxic bacteria, chemicals, and heavy metals routinely penetrate and pollute our natural water sources making people sick while exposing them to long-term health consequences such as liver damage, cancer, and other serious conditions. We have reached the point where all sources of our drinking water, including municipal water systems, wells, lakes, rivers, and even glaciers, contain some level of contamination. Even some brands of bottled water have been found to contain high levels of contaminants in addition to plastics chemicals leaching from the bottle.

A good water filtration system installed in your home is the only way to proactively monitor and ensure the quality and safety of your drinking water. Reverse osmosis water purification systems can remove 90-99% of all contaminants from the city and well water to deliver healthy drinking water for you and your family.

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