What is lime softening process?

What is lime softening process?

Lime softening (also known as lime buttering, lime-soda treatment, or Clark’s process) is a type of water treatment used for water softening, which uses the addition of limewater (calcium hydroxide) to remove hardness (deposits of calcium and magnesium salts) by precipitation.

How effective is lime softening?

The use of lime and soda ash permits hardness reduction down to 0.5 gr/gal, or about 8 ppm, as calcium carbonate. Magnesium is reduced to 2-5 ppm because of the lower solubility of magnesium hydroxide at the elevated temperatures. Hot process softening can also provide very good silica reduction.

Which lime is used for water softening?

hydrated lime
Either quicklime or hydrated lime of high calcium content can be used for water treatment. Quicklime if made from pure calcium carbonate is calcium oxide. It slakes and produces considerable heat upon the addition of water.

Which chemical is often used with lime softening?

calcium hydroxide
Lime Softening Chemicals normally used are lime (calcium hydroxide, Ca(OH)2) and soda ash (sodium carbonate, Na2CO3). Lime is used to remove chemicals that cause carbonate hardness. Soda ash is used to remove chemicals that cause non-carbonate hardness.

Why lime is used in water treatment?

Production. Lime softening is a water treatment process that uses calcium hydroxide, or limewater, to soften water by removing calcium and magnesium ions. In this process, hydrated lime is added to the water to raise its pH level and precipitate the ions that cause hardness.

How does lime soda treatment remove permanent hardness?

In this process, the hardness is removed by sedimentation as calcium carbonate or magnesium hydroxide. Lime is added either as calcium hydroxide or calcium oxide, and soda is added as sodium carbonate. The substances form hardness in water and the reactions of lime and soda can be written as follows.

What does lime treat?

Lime restores balance in overly acidic soil to bring pH back to optimal growing levels. Poor grass growth and lawn moss are signs that lawns may need lime.

Does lime softening increase pH?

The normal pH of water is between 6.5–8.5. In small systems, lime softening is typically practiced by adding hydrated lime to raw water to raise the pH to approximately 10. This removes calcium carbonate, essentially limestone. If magnesium removal is also required, the pH during softening needs to be closer to 11.

Does lime purify water?

In fact, most of the lime that is produced is used to improve the quality of drinking water as well as the water used by industry. Accordingly, lime allows water to be softened, purified, have its cloudiness eliminated, its acidity to be neutralized and its impurities to be eliminated, etc.

Does lime make water hard?

Scientists measure the hardness of water using a pH scale, which measures the hydrogen-ion concentration in the liquid. If you have an aquarium, certain types of fish will die in hard water. And a buildup of alkaline deposits (aka lime deposits) can damage plumbing and appliances like washing machines and dishwashers.

Does water softener remove alkalinity?

Disadvantages: While water softeners are good at removing hardness, they do not reduce the mineral content of the water; nor do they remove silica or alkalinity. For some boiler systems, reducing these compounds is required.

What is lime water softening?

Lime Softening. It is one of the oldest methods of water softening. The process involves the addition of lime water in the hard water. One of the primary purposes of the lime water is to soften the water as well as remove any getting rid of any bacteria that may be in the water.

What is the difference between Lime softening and ion exchange softening?

In lime softening, there is a substantial reduction in total dissolved solids (TDS). 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. COLD & WARM LIME SOFTENERS

How many molecules of lime are used in a softening reaction?

Lime Softening 2 For each molecule of calcium bicarbonate hardness removed, one molecule of lime is used. For each molecule of magnesium bicarbonate hardness removed, two molecules of lime are used. For each molecule of non-carbonate calcium hardness removed, one molecule of soda ash is used.

What are the design considerations for lime soda ash softener?

DESIGN CONSIDERATIONS. In lime soda-ash softening plants, the softening process may be carried out by a sequence of rapid mix, flocculation, and sedimentation or in a solids contactor. In the solids contactor the rapid mix, flocculation, and sedimentation occur in a single unit.