1. The purpose of re-carbonation after water softening by the lime-soda process is the

1. removal of excess soda from the water
2. removal of non-carbonate hardness in the water
3. recovery of lime from the water
4. conversion of precipitates to soluble forms in the water

2. The main disadvantages of lime soda process of water softening is that

1. It is unsuitable for turbid and acidic waters
2. Zero hardness effluent can not be obtained
3. Excessive hard water can not be softened
4. Huge amount of precipitate is formed posing the problem of disposal

3. Lime is added to water or waste water samples to

1. Destabilize colloidal oil and organic a emulsion suspension
2. Assist precipitation of metals as hydroxides by lowering their pH
3. Remove calcium hardness
4. Convert calcium carbonate

4. Zeolite process is used to

1. remove permanent hardness.
2. remove Zinc
3. remove bacteria
4. remove temporary hardness