1. Cold Lime Softening Calculations
2. Excess Lime Softening Oil
3. Excess Lime Softening
4. Lime Softening Process
5. Cold Lime Softening

Cold Lime Softening Calculations

Lime softening, also known as Clark's process,^[1] is a type of water treatment used for water softening which uses the addition of limewater (calcium hydroxide) to remove hardness (calcium and magnesium) ions by precipitation. The process is also effective at removing a variety of microorganisms and dissolved organic matter by flocculation.^[2]

Cite advantages and disadvantages of using lime softening for iron and manganese removal. Differentiate between the terms 'feeding' and 'mixing' and their relation to coagulation. Differentiate between split lime treatment and excess lime treatment. Describe the solids contact process. Lime Softening Study Guide - January 1994 Edition. Lime Soda Water Softening Process Alternatives. Three common alternative processes for lime soda water softening are i) two-stage, excess lime treatment, ii) single-stage, selective calcium removal, and iii) split treatment. Flow diagrams and a brief description of each follows. Lime-Soda Softening. After softening, the water will have high pH and contain the excess lime and the magnesium hydroxide and the calcium carbonate that did not precipitate. Recarbonation (adding carbon dioxide) is used to stabilize the water. The excess lime and magnesium hydroxide are stabilized. This article is about lime soda water softening. Lime Soda Water Softening Background. Lime soda softening uses addition of lime and soda ash to remove Ca and Mg ions, bringing their concentration down to an acceptable level. The lime may be in the form of quicklime (CaO) or hydrated lime (Ca(OH) 2), also called slaked. In lime softening, there is a substantial reduction in total dissolved solids (TDS) whereas in ion exchange softening (sometimes referred to as zeolite softening), there is no significant change in the level of TDS. Lime softening can also be used to remove iron, manganese, radium and arsenic from water. Future uses edit.

History[edit]

Lime softening was first used in 1841 to treat Thames River water. The process expanded in use as the bactericidal effect of the process was discovered. Lime softening greatly expanded in use during the early 1900s as industrial water use expanded. Lime softening provides soft water that can, in some cases, be used more effectively for heat transfer and various other industrial uses.

Chemistry[edit]

As lime in the form of limewater is added to raw water, the pH is raised and the equilibrium of carbonate species in the water is shifted. Dissolved carbon dioxide (CO₂) is changed into bicarbonate (HCO⁻
₃) and then carbonate (CO^2-
₃). This action causes calcium carbonate to precipitate due to exceeding the solubility product. Additionally, magnesium can be precipitated as magnesium hydroxide in a double displacement reaction.^[3]

In the process both the calcium (and to an extent magnesium) in the raw water as well as the calcium added with the lime are precipitated. This is in contrast to ion exchange softening where sodium is exchanged for calcium and magnesium ions. In lime softening, there is a substantial reduction in total dissolved solids (TDS) whereas in ion exchange softening (sometimes referred to as zeolite softening), there is no significant change in the level of TDS.

Virtual xp windows 7. Lime softening can also be used to remove iron, manganese, radium and arsenic from water.

Future uses[edit]

Lime softening is now often combined with newer membrane processes to reduce waste streams. Lime softening can be applied to the concentrate (or reject stream) of membrane processes, thereby providing a stream of substantially reduced hardness (and thus TDS), that may be used in the finished stream. Also, in cases with very hard source water (often the case in Midwestern USA ethanol production plants), lime softening can be used to pre-treat the membrane feed water.

Excess Lime Softening Oil

Waste products[edit]

Lime softening produces large volumes of a mixture of calcium carbonate and magnesium hydroxide in a very finely divided white precipitate which may also contain some organic matter flocculated out of the raw water. Processing or disposal of this material may be a cost to the process.

Excess Lime Softening

References[edit]

Lime Softening Process

1. ^Mellor, J W, Intermediate Inorganic Chemistry, Longmans, Green & Co, London, 1941, p. 202
2. ^USBR - Lime Softening fact sheetArchived 2011-06-13 at the Wayback Machine
3. ^'Lime Softening'. Retrieved 4 November 2011.

Cold Lime Softening