The correct answer is: A. Does not require alkalinity in water for flocculation.
Alum is a chemical compound with the formula Al2(SO4)3 · 14H2O. It is a white, odorless, crystalline solid that is commonly used as a coagulant in water treatment. Alum is a polyvalent metal salt that reacts with negatively charged particles in water to form flocs, which can then be removed by sedimentation or filtration.
The alkalinity of water is a measure of its ability to neutralize acids. Alkalinity is important in water treatment because it helps to prevent the formation of scale, which can damage pipes and equipment. Alum does not require alkalinity in water for flocculation. In fact, alum can actually increase the pH of water, which can reduce the alkalinity.
Options B, C, and D are incorrect because alum does affect the pH value of water. Alum can increase the pH of water, which can reduce the alkalinity.