Municipal Water Sodium Carbonate Treatment Methods

Water that contains a surplus of minerals is referred to as hard water. Many municipalities seek to remove minerals from their water supply if they have hard water, in order to reduce mineral buildup in pipes and other water facilities. Adding a sodium carbonate product to a water supply is one commonly used method for softening the water.

Sodium Carbonate Production

• Along with lime, sodium carbonate is one of two substances that is commonly used for the softening of supplies of hard water. It is a water-soluble substance that is also referred to as soda ash. Relatively few suppliers are certified for the production of water supply treatment-grade sodium carbonate, including 23 producers located in the contiguous United States and three production facilities located in Canada.

Dissolution Amount

• The amount of sodium carbonate that may be safely dissolved in a water supply depends on the characteristics of the product that is purchased and the density of the product. Denser sodium carbonate products are rated for dissolution of up 100 milligrams per liter or water, while lighter products are rated for dissolution of up to 667 milligrams per liter of water.

Reactions in the Water

• Once the sodium carbonate is added to water, it serves to soften the water supply by diminishing the water's mineral content. When a single molecule of sodium bicarbonate dissolves in water it results in the addition of two positive sodium ions and two carbonate, or carbon trioxide, ions to the water. These newly introduced ions combine with the calcium ions contained within the hard water, forming a solid calcium carbonate precipitate. The remaining water is "softened" due to the loss of the minerals that have solidified during this process.

  Bicarbonate ions are also added to the water in this chemical reaction. The bicarbonates are safe for human consumption and do not noticeably change the taste or other characteristics of the water, and thus they simply remain in the supply.

Calcium carbonate removal

• Once solid calcium carbonate ions have precipitated it is necessary to remove these solids from the water supply before it reaches the public. There are two primary methods for removing these ions. The first is sedimentation. This is a simple process in which the water supply is left still for a long period of time. The solid particles will settle at the bottom of the water, allowing the water to be removed from the top of the supply. The second method of calcium carbonate removal is through filtration. Filtration is a basic screening process in which the water is passed through a screen that is small enough to remove the solid particles, allowing only the softened water to pass downstream.