Tennessee Wastewater Operator Practice Exam

According to the code of federal regulations, what is not an approved method for reporting the chlorine test on the NPDES report?

1. DPD color comparator

2. DPD color metric

3. Titration method

4. Spectrophotometric analysis

The correct answer is: DPD color comparator

The DPD color comparator method is not considered an approved method for reporting chlorine test results on the National Pollutant Discharge Elimination System (NPDES) report according to the code of federal regulations. This method involves visually comparing the color of a sample with a standardized color chart, which can introduce a subjective element to the measurement. In contrast, the other methods mentioned—DPD color metric, titration, and spectrophotometric analysis—provide more precise and objective measurements of chlorine levels. DPD color metric, for example, utilizes a more sophisticated approach with specific instruments to quantify color changes more accurately. Titration methods are also recognized for their accuracy and are often used in laboratory settings to provide definitive measurements. Spectrophotometric analysis, which measures the intensity of light absorbed by the sample at a specific wavelength, aligns well with the precision requirements of environmental reporting. Each of these approved methods helps to ensure that reported data meets the stringent regulatory requirements.