California Wastewater Treatment Operator Practice Exam

A grab sample is most suited for these constituents?

1. total dissolved solids

2. dissolved oxygen

3. pH levels

4. residual chlorine

The correct answer is: residual chlorine

A grab sample is often used for measuring residual chlorine because it provides an immediate snapshot of the chlorine concentration at a specific moment in time. This is particularly important in wastewater treatment processes where residual chlorine levels need to be maintained to ensure effective disinfection before the effluent is discharged. Residual chlorine can fluctuate due to various factors in the treatment process, and a grab sample helps operators quickly assess whether the chlorine levels are within acceptable limits. Sampling at this moment captures any abrupt changes that could occur due to operational adjustments or variations in influent quality. While other parameters, such as total dissolved solids and pH levels, can also be measured using grab samples, they are typically more stable or are assessed through composite sampling methods for more accurate average concentrations over time. Dissolved oxygen levels can fluctuate rapidly as well but are often monitored continuously for more effective operation management.