Tennessee Wastewater Operator Practice Exam

In wastewater treatment, what is indicated if there is no residual ultraviolet radiation detected?

1. Effective disinfection

2. High levels of contamination

3. Ineffective treatment

4. Excessive chemical use

The correct answer is: Effective disinfection

Having no residual ultraviolet (UV) radiation detected in a wastewater treatment process typically indicates effective disinfection. This occurs because UV radiation is primarily used to deactivate harmful microorganisms in wastewater. When UV light is applied to the effluent, it alters the DNA of the pathogens, rendering them unable to reproduce and therefore non-infectious. If there is no residual UV radiation remaining after treatment, it signifies that the UV dose applied was sufficient to achieve disinfection, effectively killing or deactivating the microorganisms. This outcome is a desired condition in wastewater treatment processes, ensuring that the treated water meets safety standards before being discharged or reused. While the absence of UV radiation could theoretically suggest other issues, such as high levels of contamination or ineffective treatment, these situations generally lead to an observable presence of residual UV radiation due to failure in disinfection. Excessive chemical use is not directly related to the measurement of UV radiation either. Thus, the presence of zero residual UV radiation is a strong indicator of successful disinfection.