What occurs when suspended solids in boiler feedwater are concentrated and removed?

When suspended solids in boiler feedwater are concentrated and removed, the process referred to is coagulation. In water treatment, coagulation involves the addition of chemicals (coagulants) that help to aggregate tiny particles into larger clusters called flocs. This process makes it easier to remove these particles from the water through subsequent steps like sedimentation or filtration. The primary aim of coagulation is to reduce turbidity and improve water quality, ensuring that the boiler operates efficiently without issues that could arise from impurities.

The other processes mentioned, such as filtration, softening, and demineralization, have different purposes in treating water. Filtration is specifically focused on physically removing suspended particles, rather than the aggregation process central to coagulation. Softening addresses hardness in water by removing calcium and magnesium ions, while demineralization aims to remove all dissolved minerals or ions to produce very pure water. Hence, coagulation is the correct answer in the context of concentrating and removing suspended solids from feedwater.