California Wastewater Treatment Operator Practice Exam

How is residual chlorine typically measured in treated effluent?

1. Using a flow meter

2. Through colorimetric methods or dechlorination titration

3. By visual inspection

4. With electronic sensors

The correct answer is: Through colorimetric methods or dechlorination titration

Residual chlorine in treated effluent is typically measured using colorimetric methods or dechlorination titration. These analytical techniques are effective because they allow for the quantification of chlorine levels in a sample. Colorimetric methods involve adding specific reagents to the water sample that react with chlorine to produce a colored product. The intensity of the color formed is proportional to the concentration of residual chlorine present, allowing for accurate measurement through comparison with a standard curve or using a colorimeter. Dechlorination titration is a method that involves adding a known volume of a titrant solution to the effluent sample until the chlorine is neutralized. This process allows operators to calculate the concentration of residual chlorine based on the volume of titrant used. These methods are preferred in wastewater treatment facilities because they provide reliable and precise measurements, which are crucial for ensuring compliance with regulatory standards and for effective treatment operations. They also help prevent the negative environmental impacts that can arise from excess chlorine in discharged effluent. Using a flow meter, conducting visual inspections, or employing electronic sensors are less effective or not suitable for accurately measuring residual chlorine concentrations in treated effluent. Flow meters monitor the volume of water but do not assess chemical components, visual inspections are subjective and cannot provide quantitative