In a precipitative softening plant, what percentage of solids is typically produced?

• A. 1%
• B. 3%
• C. 5%
• D. 10%

Answer: (C)

In a precipitative softening plant, the production of solids, typically known as sludge, is an important aspect of the water treatment process. The correct answer indicates that around 5% of the total solids are produced during precipitation reactions involving hardness ions, such as calcium and magnesium.

This percentage reflects the efficiency of the process where calcium carbonate is formed and subsequently removed from the water as solid particles. As water undergoes softening, the dissolved salts are converted into solids, which can be collected and disposed of or treated further.

Understanding this percentage is crucial for operators because it impacts sludge handling practices and overall plant operations. It's also significant for the environmental considerations related to the disposal of sludge, as higher concentrations may require more advanced management strategies.

The other percentages represent lower or higher expectations for solid production relative to what is typically observed in these plants under standard operating conditions.