Which compound is commonly used to control algae growth?

Copper sulfate is commonly used to control algae growth in water bodies. It acts as an algicide, effectively targeting various species of algae, which can lead to harmful water conditions if allowed to proliferate. Copper ions disrupt the photosynthesis process in algae and inhibit their growth, making it a popular choice for managing algal blooms in reservoirs, lakes, and ponds.

This method is particularly valuable in recreational water bodies and drinking water supplies where controlling algae is necessary to maintain water quality and prevent issues like taste and odor problems, as well as the potential for toxic compounds produced by certain types of algae. The application of copper sulfate should always be done with care and consideration of environmental regulations to avoid harming non-target aquatic life.

The other options do have their roles in water treatment and management, but they are not primarily used for algae control. Chlorine is commonly used for disinfection rather than targeting algae specifically, alum is mainly used for coagulation and sedimentation processes, and calcium carbonate serves primarily to adjust water hardness and alkalinity, with limited effects on algae growth.