California Wastewater Treatment Operator Practice Exam

The effectiveness of disinfection is determined by:

1. the presence of algae in the water

2. the turbidity level of the effluent

3. the coliform concentration in the effluent

4. the pH of the disinfectant used

The correct answer is: the coliform concentration in the effluent

The effectiveness of disinfection in wastewater treatment is primarily determined by the coliform concentration in the effluent. Coliform bacteria are indicators of fecal contamination and, by extension, the potential presence of harmful pathogens. Monitoring coliform concentration allows operators to assess whether the disinfection process has effectively reduced the levels of bacteria to acceptable standards, ensuring that the treated water is safe for discharge or reuse. Other factors, such as turbidity and pH, can influence disinfection but do not directly measure its effectiveness in terms of microbial reduction. For instance, high turbidity can shield microorganisms from the disinfectant, potentially leading to insufficient disinfection, but it does not measure the actual disinfection outcome. Similarly, while the pH of the disinfectant can affect its efficacy, it is not a direct indicator of how well disinfection has been achieved in the effluent.