The temperature versus DO relationship for wastewater is such:

The temperature versus DO relationship for wastewater is such:

• A. Higher the temperature, the higher the DO saturation level
• B. Higher the temperature, the lower the DO saturation level
• C. Lower the temperature, the lower the DO saturation level
• D. None of the above

Answer: (B)

Temperature controls how much oxygen water can hold above saturation. Warmer water holds less dissolved oxygen, so the saturation level decreases as temperature rises. This happens because gas solubility in liquids falls with increasing temperature—the molecules have more energy and are more prone to escape into the air. In wastewater, that means at higher temperatures you reach a lower maximum DO concentration than at cooler temperatures, making it harder to maintain adequate dissolved oxygen. So, higher temperature leads to a lower DO saturation level.

Temperature controls how much oxygen water can hold above saturation. Warmer water holds less dissolved oxygen, so the saturation level decreases as temperature rises. This happens because gas solubility in liquids falls with increasing temperature—the molecules have more energy and are more prone to escape into the air. In wastewater, that means at higher temperatures you reach a lower maximum DO concentration than at cooler temperatures, making it harder to maintain adequate dissolved oxygen. So, higher temperature leads to a lower DO saturation level.