Water Softening System Operation

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Questions and Answers

What is the main reason for water to be considered hard?

Presence of dissolved bicarbonates

Which type of hardness can be easily removed by heating?

Temporary hardness

What causes permanent hardness in water?

Sulphates and chlorides of calcium and magnesium

Why is it important to remove or treat dissolved solids like calcium and magnesium before water enters a boiler system?

To prevent scale formation and lower heat transfer efficiency Signup and view all the answers

What concentration of calcium or magnesium ions classifies water as hard?

Over 120 ppm (120 mg/L) Signup and view all the answers

Which method is NOT effective for removing permanent hardness from water?

Boiling the water Signup and view all the answers

What are the main concerns for consumers regarding hard water?

Less likelihood to lather well and white residue on faucets and dishware Signup and view all the answers

What is the purpose of the lime-soda softening process?

To remove harmful ions from water Signup and view all the answers

In the lime-soda softening process, what reacts with the impurities causing carbonate hardness?

Lime and soda ash Signup and view all the answers

What is a characteristic of hot lime-soda softening process compared to the cold process?

It can remove silica while the cold process cannot Signup and view all the answers

What is the function of zeolite softeners in water treatment?

To remove hardness-causing calcium and magnesium ions using ion exchange Signup and view all the answers

What is a benefit of using ion-exchange zeolite softeners compared to lime-soda softeners?

They are easier to control and have safer chemicals for operators Signup and view all the answers

What type of ions replace scale-forming magnesium and calcium ions in an ion exchange softener?

Sodium ions Signup and view all the answers

What is a characteristic of zeolite softeners in terms of removing hardness from water?

They can bring the hardness down to zero Signup and view all the answers

What is the purpose of backwashing in a zeolite softener?

To expand the volume of the bed and remove entrained dirt Signup and view all the answers

What is the purpose of brining in a zeolite softener?

To remove calcium and magnesium from the zeolite material Signup and view all the answers

What happens during slow rinse in a zeolite softener?

Water flows downwards creating a slow moving plug of water Signup and view all the answers

Why should the backwash flow not be too fast in a zeolite softener?

To avoid carrying out zeolite resin with the backwash effluent Signup and view all the answers

What can cause a reduction in the capacity of a softener or incomplete softening?

Fouled exchange material Signup and view all the answers

What is a potential result of excessive flow during backwash in a zeolite softener?

Loss of zeolite material Signup and view all the answers

How can improper flow rates affect the operation of a zeolite softener?

Causing incomplete softening of the water Signup and view all the answers

What is the purpose of periodic replacement of the zeolite resin?

To regenerate the ion exchangers Signup and view all the answers

What is the effluent of the cation exchanger in the demineralizer?

An acidic solution Signup and view all the answers

What happens during the regeneration of the cation exchanger in the ion exchangers?

Calcium ions are released and replaced by sodium ions Signup and view all the answers

What is the main purpose of reverse osmosis (RO)?

To desalinate sea water Signup and view all the answers

How does reverse osmosis differ from regular osmosis?

Reverse osmosis applies pressure to separate impurities Signup and view all the answers

In a demineralizer, what happens in the anion exchanger?

Anions are exchanged for hydroxide ions Signup and view all the answers

What is the standard range for the conductivity reading of water after treatment by demineralizers?

Between 15-30 μS/cm Signup and view all the answers

How are ion exchangers in demineralizers regenerated when exhausted?

By using a diluted solution of sulfuric acid for both exchangers Signup and view all the answers

What total dissolved solids (TDS) value does sea water typically have?

38000 Signup and view all the answers

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