Tennessee Wastewater Operator Practice Exam

What color indicates a properly functioning facultative lagoon that receives domestic sewage?

1. Light green

2. Dark blue

3. Yellow

4. Deep green

The correct answer is: Deep green

A properly functioning facultative lagoon that receives domestic sewage typically exhibits a deep green color. This coloration is primarily due to the presence of algae, which thrive in the nutrient-rich conditions provided by the breakdown of organic matter from the sewage. This deep green hue indicates that the lagoon is effectively performing its biological treatment function, where algae play an essential role in the process by contributing oxygen through photosynthesis and providing a surface for microbial activity. The other color options represent different conditions that may indicate malfunctions or nutrient imbalances within the lagoon. For example, light green might suggest insufficient algal growth, dark blue could indicate a lower level of biological activity or nutrient deficiency, and yellow may point toward higher levels of nutrient overload or the presence of non-ideal conditions conducive to other processes. Therefore, the deep green color is a strong indicator of a healthy and effective facultative lagoon environment.