Which of the following wastewater streams comes from cooling towers?

The correct answer is the blow down from cooling towers. This wastewater stream is a result of the concentration of dissolved solids and other impurities in the cooling water that occurs during the cooling process. As cooling towers operate, some water is lost to evaporation, leading to an increase in the concentration of these impurities. To maintain efficiency and prevent scaling or biological growth within the system, a portion of this concentrated water is removed or "blown down." This blowdown serves to manage water quality and maintain the operational integrity of the cooling system.

Other options refer to different sources of wastewater. For instance, waste from floor drains generally comes from facility maintenance and does not pertain to cooling processes. Boiler blowdown is related to steam boiler operations aimed at controlling the concentration of dissolved solids; although it is a wastewater stream, it is distinct from that of cooling towers. Waste from demineralizers arises from the purification of water for use in various industrial processes, again making it unrelated to the cooling tower function.

Understanding the nature and source of these wastewater streams is essential for proper water management and treatment in industrial settings.